Obscured feature detector with pattern matching

ABSTRACT

A surface-conforming obscured feature detector includes a plurality of sensor plates, each having a capacitance that varies based on the dielectric constant of the materials that compose the surrounding objects and the proximity of those objects. A sensing circuit is coupled to the sensor plates  32  to measure the capacitances of the sensor plates. A controller is coupled to the sensing circuit to analyze the capacitances measured by the sensing circuit. One or a plurality of indicators are coupled to the controller, and are selectively activated to identify the location of an obscured feature behind a surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of the following patent applications:U.S. Provisional Patent Application No. 61/339,316, entitled “MATERIALDETECTOR THAT OPERATES FROM A STATIONARY POSITION” and filed on Mar. 4,2010; U.S. Provisional Patent Application No. 61/333,252, entitled“MATERIAL DETECTOR THAT OPERATES FROM A STATIONARY POSITION” and filedon May 10, 2010; U.S. Provisional Patent Application No. 61/345,591,entitled “MATERIAL DETECTOR THAT OPERATES FROM A STATIONARY POSITION”and filed on May 17, 2010; U.S. Provisional Patent Application No.61/433,954, entitled “OBSURED FEATURE DETECTOR” and filed on Jan. 18,2011; U.S. Provisional Patent Application No. 61/436,188, entitled“OBSCURED FEATURE DETECTOR” and filed on Jan. 25, 2011. This applicationis a continuation-in-part of U.S. Non-Provisional patent applicationSer. No. 12/826,478 entitled “STATIONARY FEATURE DETECTOR” and filed onJun. 29, 2010; and a continuation-in-part of U.S. Non-Provisional patentapplication Ser. No. 12/860,448 entitled “SURFACE-CONFORMING OBSUREDFEATURE DETECTOR” and filed on Aug. 20, 2010. The entire contents ofthese patent applications are incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates generally to devices used for detectingthe presence of obscured features behind opaque, solid surfaces, morespecifically, devices used for locating beams and studs behind walls andjoists beneath floors.

2. Background

The need to locate obscured features such as beams, studs, joists andother support elements behind walls and beneath floors is a commonproblem encountered during construction, repair and home improvementactivities. Often a need exists to cut or drill into a supported surfacewith the aim of creating an opening in the surface while avoiding theunderlying support elements. In these instances, it is desirable to knowwhere the support elements are positioned before beginning so as toavoid cutting or drilling into them. On other occasions, one may desireto anchor a heavy object to the obscured support element. In thesecases, it is often desirable to install a fastener through the surfacein alignment with the underlying support element. However, once thewall, floor or surface is in place, the location of the support elementis not visually detectable

A variety of rudimentary techniques have been employed with limitedsuccess to address this problem in the past. These have included drivingsmall pilot nails through the surface until a support element isdetected and then covering over holes in the surface that did not revealthe location of the stud or support. A less destructive techniquecomprises tapping on the surface in question with the aim of detectingaudible changes in the sound which emanates from the surface when thereis a support element beneath or behind the area being tapped. Thistechnique is not very effective, however, because the accuracy of theresults depends greatly on the judgment and skill of the personsearching for the support, and because the sound emitted by the tappingis heavily influenced by the type and density of the surface beingexamined.

Magnetic detectors have also been employed to find obscured supportelements with the detector relying on the presence of metallicfasteners, such as nails or screws, in the wall and support element totrigger a response in the detector. However, since metallic fastenersare spaced at discrete locations along the length of a support, amagnetic detector may pass over a length of the support where nofasteners are located, thereby failing to detect the presence of theobscured support element.

Capacitive sensors have also been employed to detect obscured featuresbehind opaque surfaces. These detectors sense changes in capacitance onthe examined surface that result from the presence of featurespositioned behind, beneath or within the surface. These changes incapacitance are detectable through a variety of surfaces such as wood,sheet-rock, plaster, gypsum and do not rely on the presence of metalfasteners in the surface or obscured feature for activation of thesensor.

However, conventional capacitive sensors often suffer from a number ofshortcomings. For example, conventional capacitive sensors typicallyrequire movement across an examined surface, sometimes repeatedly, toeffectively locate an obscured feature or support element. In addition,capacitive sensors generally can only locate one feature at a time, andoften can only find the edge of the feature rather than its centerpoint. Some capacitive sensors rely on an assumed width of a feature tocalculate the location of the center of the feature based on detectionof the edge. Such devices frequently require a comparison circuit inaddition to a sensing circuit in order to compare capacitances sensed bydifferent sensors.

SUMMARY

The present disclosure advantageously addresses one or more of theaforementioned deficiencies in the field of obscured feature detectionby providing an accurate, simple to use and inexpensively manufacturedobscured feature detector. The detector can be employed by placing thedevice against the examined surface and reading the location of allfeatures present beneath the surface where the device is positioned.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plate to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe sensor plates, the circuit being configured to measure thecapacitances of the sensor plates, the set of measured capacitancevalues comprising a measured reading pattern. The obscured featuredetector further comprises a pattern matching module configured tocompare the measured reading pattern with a plurality of predeterminedpatterns and determine which predetermined pattern best matches themeasured reading pattern, and one or a plurality of indicators coupledto the controller, each indicator capable of toggling between adeactivated state and an activated state. The controller is configuredto activate one or more of the indicators to identify a location of anobscured feature.

At least one of the predetermined patterns may have values that areconsistent with the detector performing a reading on sheetrock with asingle stud behind the sheetrock. At least one of the predeterminedpatterns may have values that are consistent with the detectorperforming a reading on sheetrock with two studs behind the sheetrock,the two studs separated by a distance of at least about two inches. Theobscured feature detector may comprise at least four sensor plates. Theindicators may be LEDs. The pattern matching module may be configured tocompare the values of the measured reading pattern to the values of apredetermined pattern. The pattern matching module may be configured tocompare the slopes of the measured reading pattern to the slopes of apredetermined pattern, wherein the slopes of the measured readingpattern may be calculated by comparing neighboring measured capacitancevalues and the slopes of the predetermined pattern may be calculated bycomparing neighboring values. The plurality of predetermined patternsmay comprise at least 30 unique patterns. Each of the sensor plates maybe substantially the same size. The plurality of predetermined patternsmay include multiple patterns corresponding to a single stud, where eachof the multiple patterns may correspond to a single stud in a differentlocation. The obscured feature detector may comprise a non-volatilememory that stores the plurality of sensor read patterns. The patternmatching module may be configured to calculate the plurality of sensorread patterns and store them in memory when the obscured featuredetector is initialized. The pattern matching module may be configuredto calculate the plurality of sensor read patterns and store them inmemory when a calibration routine in executed. Finally, the patternmatching module may be configured to calculate the plurality of sensorread patterns in real-time, when the obscured feature detector is inuse.

In one embodiment, a method for determining the location of obscuredfeatures behind a surface comprises placing an obscured feature detectoron the surface, the obscured feature detector having a plurality ofsensor plates arranged in an array, measuring capacitance readingssensed in a plurality of regions, each region corresponding to an areasurrounding one or more of the sensor plates, the set of capacitancereadings forming a measured reading pattern. The method includes thestep of comparing the measured reading pattern to each of a plurality ofpredetermined patterns, each predetermined pattern comprising a set ofvalues, identifying, based upon comparisons of the measured readingpattern to the predetermined patterns, the predetermined pattern thatbest matches the measured reading pattern, and each predeterminedpattern being associated with one or more indicators. The method alsocomprises the step of activating the one or more indicators associatedwith the predetermined pattern that best matches the measured readingpattern.

At least one of the predetermined patterns may have values that areconsistent with the detector performing a reading on sheetrock with asingle stud behind the sheetrock. At least one of the predeterminedpatterns may have values that are consistent with the detectorperforming a reading on sheetrock with two studs behind the sheetrock,the two studs being located adjacent to each other. At least one of thepredetermined patterns may have values that are consistent with thedetector performing a reading on sheetrock with two studs behind thesheetrock, the two studs being separated by a distance of at least abouttwo inches. At least one predetermined pattern may be associated withone or more indicators spanning a distance of at least about one and onehalf inches. And at least one predetermined pattern may be associatedwith one or more indicators that indicate the edges of an obscuredfeature.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plate to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe sensor plates, the circuit being configured to measure thecapacitances of the sensor plates, a controller coupled to the sensingcircuit, the controller being configured to analyze the capacitancesmeasured by the sensing circuit, and one or more indicators coupled tothe controller, each indicator capable of toggling between a deactivatedstate and an activated state. When the controller detects two or moreobscured features, the controller is configured to activate two or moreindicators simultaneously to identify the locations of the two or moreobscured features.

The detector may be at least approximately seven inches wide. The numberof sensor plates may be 4 or greater. Each of the sensor plates may besubstantially the same size. The detector may be capable of detectingthree or more features simultaneously. The detector may be capableidentifying the width of more than one feature. The obscured featuredetector may further comprise a pattern matching module that may beconfigured to compare the measured capacitance readings with a pluralityof predetermined patterns and determine which predetermined pattern bestmatches the measured capacitance readings.

In another embodiment, a method for determining the location of aplurality of obscured features behind a surface comprises placing anobscured feature detector on the surface, the obscured feature detectorhaving a plurality of sensor plates arranged in an array, measuringcapacitance readings sensed in a plurality of regions, each regioncorresponding to an area surrounding one or more of the sensor plates,identifying, based upon the measured capacitance readings, the locationof the plurality of obscured features, and activating a plurality ofindicators simultaneously to identify the locations of the plurality ofobscured features.

Identifying the location of the plurality of obscured features maycomprise using a pattern matching module to determine the locations ofthe plurality of obscured features.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plate to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe sensor plates, the circuit being configured to measure thecapacitances of the sensor plates, a controller coupled to the sensingcircuit, the controller being configured to analyze the capacitancesmeasured by the sensing circuit, and one or more indicators coupled tothe controller, each indicator capable of toggling between a deactivatedstate and an activated state. The controller is configured to activateone or more of the indicators to identify both a location and a width ofan obscured feature.

The detector may use a pattern matching module to determine the width ofobscured features. The detector may activate indicators that are infront of an obscured feature to indicate the width of the obscuredfeatures. A larger number of activated indicators may indicate that anobscured feature is wider, and a smaller number of activated indicatorsmay indicate that an obscured feature is narrower.

In another embodiment, an obscured feature detector comprises aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plate to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The obscured feature detector further comprises a sensingcircuit coupled to the sensor plates, the circuit being configured tomeasure the capacitances of the sensor plates, a controller coupled tothe sensing circuit, the controller being configured to analyze thecapacitances measured by the sensing circuit, and one or a plurality ofindicators coupled to the controller, each indicator capable of togglingbetween a deactivated state and an activated state. The controller isconfigured to activate one or more of the indicators to identify alocation of an obscured feature such that indicators that are in frontof an obscured feature are activated.

In another embodiment, a method for determining the location of morethan one obscured features behind a surface comprises placing anobscured feature detector on the surface, the obscured feature detectorhaving a plurality of sensor plates arranged in an array, measuringcapacitance readings sensed in a plurality of regions, each regioncorresponding to an area surrounding one or more of the sensor plates,identifying, based upon the measured capacitance readings, the locationof an obscured feature, and activating the indicator(s) in front of theobscured feature to identify both the location and the width of theobscured feature.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plate to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe sensor plates, the circuit being configured to measure thecapacitances of the sensor plates, a controller coupled to the sensingcircuit, the controller being configured to analyze the capacitancesmeasured by the sensing circuit, and one or more indicators coupled tothe controller, each indicator capable of toggling between a deactivatedstate and an activated state. The controller is configured to activateone or more of the indicators to identify both a location and a width ofan obscured feature, and the controller is configured to detectelectromagnetic fields.

The sensing circuit may be configured to perform capacitive readings ata frequency that is higher than the electromagnetic field frequencydetected by the sensor plates. The sensing circuit may be configured toperform capacitive readings at a frequency that is an inharmonic of theelectromagnetic field frequency detected by the sensor plates. Thesensing circuit may be configured to perform capacitive reads at least150 times per second. The controller may be configured to comparemultiple capacitive readings associated with a given region to calculatethe amount of disparity in the readings. The obscured object detectormay be configured such that regions with greater disparity of readingsas compared to the detector's other regions, are identified as regionsthat are closer to an alternating electromagnetic field. The detectormay further comprise a disparity reading pattern that may be defined bythe a plurality of the disparity readings, and a pattern matching modulethat may be configured to compare the disparity reading pattern with aplurality of predetermined patterns to determine which predeterminedpattern best matches the disparity reading pattern. The controller maybe optimized to detect electromagnetic fields with a frequency ofapproximately 50 to 60 Hz. The obscured feature detector may comprise atleast four sensor plates.

In one embodiment, a method for determining the location of analternating electromagnetic field comprises placing an electromagneticfield detector on a surface, the electromagnetic field detector having aplurality of sensor plates arranged in an array, taking capacitancereadings in an area surrounding one or more of the sensor plates,identifying, based upon the capacitance readings, the location of one ora plurality of alternating electromagnetic fields, and activating one ora plurality of indicators to promote visual identification of thelocation of an alternating electromagnetic field.

Capacitive readings may be taken at a higher frequency than thefrequency of the detected electromagnetic field(s). Capacitive readingsmay be taken at a frequency that is an inharmonic of the frequency ofthe detected electromagnetic field(s). Capacitive readings may be takenat least 150 times per second. Multiple capacitive readings from asingle area may be compared to each other to determine disparity factorsrepresenting the amount of disparity in the capacitive readings. Areaswith more disparity in the readings may be identified as areas that arecloser to an alternating electromagnetic field. Values that representthe disparity in the capacitance readings may define a disparity readingpattern, and the disparity reading pattern may be compared to aplurality of predetermined patterns to identify the predeterminedpattern that best matches the disparity reading pattern. And the arrayof sensor plates may comprise at least four sensor plates.

In another embodiment, an obscured feature detector comprises aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plates to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The obscured feature detector further comprises a sensingcircuit coupled to the sensor plates by a plurality of electricallyconductive paths, the sensing circuit being configured to measure thecapacitances of the sensor plates, the electrically conductive pathshaving a length defined by the distance along the paths between thesensor plates and the sensing circuit, and two or more of theelectrically conductive path lengths are substantially the same.

Two or more of the electrically conductive paths may have a width whichis substantially the same. The electrically conductive paths maycomprise a first segment and a second segment, wherein the first segmentmay have a constant first width, and the second segment may have aconstant second width. Each of the sensor plates may have a lengthdefined by the distance from a first surface to an opposite secondsurface of a plate, and each sensor plate may have substantially thesame length. Each of the sensor plates may have a width defined by thedistance from a third surface to an opposite fourth surface of a plate,and each sensor plate may have substantially the same width. Each of thesensor plates may have a thickness defined by the distance from a topsurface to a bottom surface of a plate, and each sensor plate may havesubstantially the same thickness. A portion of the electricallyconductive path may comprise a copper trace on a printed circuit board.The obscured feature detector may further comprise a controller coupledto the sensing circuit, the controller being configured to analyze thecapacitance in the area surrounding each sensor plate measured by thesensing circuit, and one or a plurality of indicators may be coupled tothe controller, each indicator capable of toggling between a deactivatedstate and an activated state. The controller may be configured toactivate one or more of the indicators to identify a location of anobscured feature.

In another embodiment, a method of using an obscured feature detectorhaving a plurality of sensor plates to determine the location of anobscured feature behind a surface comprises placing the obscured featuredetector on the surface, transmitting a value from the plurality ofsensor plates along a plurality electrically conductive paths to asensor circuit, wherein the length of at least two of the conductivepaths is substantially equal, measuring capacitance readings sensed in aplurality of regions, each region corresponding to an area surroundingone or more of the sensor plates and represented by the valuetransmitted from the plurality of sensor plates, and identifying, basedon the capacitance readings, a location of the obscured feature behindthe surface.

The method may further comprise activating one or more indicators toindicate the location of the obscured feature behind the surface. Thesensor plates may each have a length that is substantially the same. Thesensor plates may each have a width that is substantially the same. Thesensor plates may each have a thickness that is substantially the same.A portion of the electrically conductive path may comprise a coppertrace on a printed circuit board. A first segment of an electricallyconductive path may be located on a first layer of a printed circuitboard, and a second segment of an electrically conductive path may belocated on a second layer of a printed circuit board. Two or more of theelectrically conductive paths may have substantially the same width. Andthe electrically conductive paths may have a first segment and a secondsegment; the first segment may have a substantially constant firstwidth, and the second segment may have a substantially constant secondwidth.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plates to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe sensor plates via a plurality of sensor plate traces, the sensingcircuit being configured to measure the capacitance of each of thesensor plates, and a plurality of shield traces located adjacent to thesensor plate traces and configured to provide a substantially uniformelectrical environment for two or more of the sensor plate traces.

The obscure feature detector may further comprise a controller coupledto the sensing circuit, the controller may be configured to analyze thecapacitances measured by the sensing circuit, one or a plurality ofindicators may be coupled to the controller, and each indicator may becapable of toggling between a deactivated state and an activated state.The controller may be configured to activate one or more of theindicators to identify a location of an obscured feature. The shieldtraces may be substantially parallel to the sensor plate traces. Theshield traces may be positioned such that the shield traces shield thesensor plate traces from external electromagnetic fields. Each sensorplate trace may have one or more respective shield traces. The sensorplate traces and shield traces may be positioned such that capacitancebetween each sensor plate trace and each shield trace is substantiallythe same for each sensor plate trace and its respective shield trace. Asensor plate trace may be accompanied by two shield traces, such thatone shield trace is positioned on each side of the sensor plate trace. Asensor plate trace and a shield trace may be positioned such that thereis a constant distance between a sensor plate trace and the respectiveshield trace, along their length. Each of the shield traces may bepositioned at a uniform distance away from the respective sensor platetrace. A segment of the each sensor plate trace and a segment of eachshield trace may comprise copper traces on a printed circuit board. Thesensor plate traces and shield traces may both be located on the samelayer of a printed circuit board. The shield traces may be driven at afixed voltage level. And the shield traces may be driven at a voltagethat is similar to the voltage driven on the sensor plate traces.

In one embodiment, an obscured feature detector comprises an array of aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plates to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The obscured feature detector may further comprise a sensingcircuit coupled to the sensor plates, the sensing circuit beingconfigured to measure the capacitance of each of the sensor plates, anda controller coupled to the sensing circuit, the controller beingconfigured to analyze the capacitances measured by the sensing circuit.The array of sensor plates and the sensing circuit is supported by ahousing that includes a gripping surface, the array of sensor plates arearranged in series, and the gripping surface is largely parallel to thearray of sensor plates such that the array of sensor plates and thegripping surface are largely parallel. The obscured feature detectorfurther comprises one or a plurality of indicators coupled to thecontroller, each indicator capable of toggling between a deactivatedstate and an activated state, and the controller is configured toactivate one or more of the indicators to identify a location of anobscured feature.

The gripping surface may be oriented such that when the detector is heldon a wall in a position to detect vertical studs, four or more fingersare lined up with an orientation that is more horizontal than vertical.The housing may comprise plastic, and the gripping surface may comprisean elastomer. The gripping surface may be a curved surface, and it mayalso be a flat surface.

In one embodiment, a method for using an obscured object detector with aplurality of sensor plates to detect an object behind an obscuringsurface comprises orienting the obscured object detector on theobscuring surface such that the plurality of sensor plates define anarray that is substantially horizontal, and gripping the obscured objectdetector on a predefined gripping region defined on an exterior surfaceof the obscured object detector, wherein the gripping regions aresubstantially parallel to the sensor plate array.

In another embodiment, an obscured feature detector comprises aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plates to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The detector has a housing comprising a bottom portion thathouses the plurality of sensor plates. A layer of material is attachedto the bottom portion of the detector, wherein the material comprisesplastic.

The obscured feature detector may further comprise a sensing circuitcoupled to the sensor plates, the sensing circuit being configured tomeasure the capacitances of the sensor plates, a controller coupled tothe sensing circuit, the controller being configured to analyze thecapacitances measured by the sensing circuit, and/or one or a pluralityof indicators coupled to the controller, each indicator capable oftoggling between a deactivated state and an activated state. Thecontroller may be configured to activate one or more of the indicatorsto identify a location of an obscured feature. And the layer of materialmay comprise ultra-high molecular weight polyethylene.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plates to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe plurality of sensor plates, the sensing circuit being configured tomeasure the capacitance of each of the sensor plates, and a controllercoupled to the sensing circuit, the controller being configured toreceive the capacitance measurements from the sensing circuit. Thecontroller is configured to operate in a first mode and a second mode,the first mode configured to detect obscured features of a predeterminedfirst material, and the second mode configured to detect obscuredfeatures of a predetermined second material. One or a plurality ofindicators are coupled to the controller, each indicator capable oftoggling between a deactivated state and an activated state, and thecontroller is configured to activate one or more of the indicators toidentify a location of an obscured feature.

The first predetermined material may be wood. The second predeterminedmaterial may be metal or plastic. A measured reading pattern may bedefined by a set of measured capacitance values, the first modeconfigured to use a pattern matching module, the pattern matching modulebeing configured to compare the measured reading pattern with aplurality of predetermined patterns to identify the predeterminedpattern that best matches the measured reading pattern. One or more ofthe predetermined patterns may have capacitance values representingobscured features that comprise wood. The second mode may be configuredto use a pattern matching module, the pattern matching module beingconfigured to compare the measured reading pattern with a plurality ofpredetermined patterns to identify the predetermined pattern that bestmatches the measured reading pattern, and one or more of thepredetermined patterns may have capacitance values representing obscuredfeatures that comprise metal. The first mode, or second mode, can beselected via an actuator. The controller may select the mode ofoperation, or the controller may automatically select the mode. Thecontroller may also automatically select the mode after the capacitanceshave been measured.

In one embodiment, a method for determining the location of an obscuredfeature behind a surface comprises selecting a first mode or a secondmode of an obscured feature detector, the first mode being configured todetect obscured features of a predetermined first material and thesecond mode being configured to detect obscured features of apredetermined second material, placing the obscured feature detector onthe surface, the obscured feature detector having a plurality of sensorplates arranged in an array, and sensing the capacitance in an areasurrounding one or more of the sensor plates. The method also comprisesthe step of identifying, based upon the sensed capacitance, the locationof one or a plurality of obscured features, and activating one or aplurality of indicators to promote visual identification of the locationof an obscured feature.

The step of selecting a mode may comprise selecting a wood or wood-likematerial mode. The step of selecting a mode may comprise selecting ametal or metal-like material mode. The set of measured capacitancevalues may comprise a measured reading pattern, and comparing, using thefirst mode, the measured reading pattern with a plurality ofpredetermined patterns to identify the predetermined pattern that bestmatches the measured reading pattern. One or more of the predeterminedpatterns may have capacitance values representing obscured features thatcomprise wood. A measured reading pattern may be defined by a set ofmeasured capacitance values, and comparing, using the second mode, themeasured reading pattern with a plurality of predetermined patterns toidentify the predetermined pattern that best matches the measuredreading pattern. One or more of the predetermined patterns may havecapacitance values representing obscured features that comprise metal.Selecting the mode may be performed via a switch, a controller,automatically by a controller, and/or automatically after thecapacitances have been measured.

In another embodiment, an obscured feature detector comprises aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plates to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The obscured feature detector further comprises a sensingcircuit coupled to the plurality of sensor plates, the sensing circuitbeing configured to measure the capacitance in the area surrounding eachof the sensor plates, and a controller coupled to the sensing circuit,the controller being configured to analyze the capacitances measured bythe sensing circuit. The controller is configured to operate in a firstmode and a second mode, the first mode to detect obscured featuresthrough a first predetermined surface material, and the second mode todetect obscured features through a second predetermined surfacematerial. The obscured feature detector further comprises one or aplurality of indicators coupled to the controller, each indicatorcapable of toggling between a deactivated state and an activated state,and the controller is configured to activate one or more of theindicators to identify a location of an obscured feature.

The first surface material may be wood. The second surface material maybe sheetrock, concrete, and/or tile. A measured reading pattern may bedefined by a set of measured capacitance values. The first mode may beconfigured to use a pattern matching module, the pattern matching modulebeing configured to compare the measured reading pattern with aplurality of predetermined patterns to identify the predeterminedpattern that best matches the measured reading pattern. One or more ofthe predetermined patterns may have capacitance values that represent awood or wood-like surface, and/or a sheetrock or sheetrock-like surface.The mode can be selected via a switch, the controller, or automaticallyby the controller.

In another embodiment, a method for locating an obscured feature behinda surface comprises selecting a first mode or a second mode of anobscured feature detector, the first mode being configured to detectobscured features through a predetermined first material and the secondmode being configured to detect obscured features through apredetermined second material, placing the obscured feature detector onthe surface, the obscured feature detector having a plurality of sensorplates arranged in an array, sensing the capacitance in an areasurrounding one or more of the sensor plates, and identifying, basedupon the sensed capacitance, the location of one or a plurality ofobscured features. The method further comprises the step of activatingone or a plurality of indicators to promote visual identification of thelocation of an obscured feature.

The step of selecting a mode may comprise selecting a wood or wood-likematerial mode. The step of selecting a mode may comprise selecting asheetrock or sheetrock-like material mode. A measured reading patternmay be defined by a set of measured capacitance values, and comparing,using the first mode, the measured reading pattern with a plurality ofpredetermined patterns to identify the predetermined pattern that bestmatches the measured reading pattern, and further wherein one or more ofthe predetermined patterns has capacitance values representing a surfacematerial that comprises wood or metal.

In yet another embodiment, an obscured feature detector comprises aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plates to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The obscured feature detector further comprises a sensingcircuit coupled to the plurality of sensor plates, the sensing circuitbeing configured to measure the capacitance of each of the sensorplates, a controller coupled to the sensing circuit, the controllerbeing configured to receive the capacitance measurements from thesensing circuit, the controller configured to operate in a first modeand a second mode, and the first mode configured to detect a singlefeature, and the second mode configured to be a normal operation mode.One or a plurality of indicators are coupled to the controller, eachindicator capable of toggling between a deactivated state and anactivated state, and the controller is configured to activate one ormore of the indicators to identify a location of an obscured feature.

In another embodiment, a method for determining the location of anobscured feature behind a surface comprises selecting a first mode or asecond mode of an obscured feature detector, the first mode beingconfigured to detect a single obscured feature and the second mode beingconfigured to be a normal mode of operation, placing the obscuredfeature detector on the surface, the obscured feature detector having aplurality of sensor plates arranged in an array, sensing the capacitancein an area surrounding one or more of the sensor plates, andidentifying, based upon the sensed capacitance, the location of one or aplurality of obscured features. The method further comprises the step ofactivating one or a plurality of indicators to promote visualidentification of the location of an obscured feature.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plates to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe plurality of sensor plates, the sensing circuit being configured tomeasure the capacitance of each of the sensor plates, a controllercoupled to the sensing circuit, the controller being configured toreceive the capacitance measurements from the sensing circuit, thecontroller configured to operate in a first mode and a second mode, andthe first mode configured to detect obscured features that are at leasta first distance behind a surface, and the second mode configured todetect obscured features that are less than the first distance behindthe surface. One or a plurality of indicators are coupled to thecontroller, each indicator capable of toggling between a deactivatedstate and an activated state, and the controller is configured toactivate one or more of the indicators to identify a location of anobscured feature.

The first distance may be ¾″ or 1″. A measured reading pattern may bedefined by a set of measured capacitance values, the first modeconfigured to use a pattern matching module, the pattern matching modulebeing configured to compare the measured reading pattern with aplurality of predetermined patterns to identify the predeterminedpattern that best matches the measured reading pattern. One or more ofthe predetermined patterns may have values representing an obscuredfeature depth of at least ¾″ or at least 1″. More than one capacitancereadings from an area may be combined to determine a value of themeasured reading pattern. The first mode may combine more capacitancereadings to determine a value of the measured reading pattern, and thesecond mode may combine fewer capacitance readings to determine a valueof the measured reading pattern.

In another embodiment, an obscured feature detector comprises aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plates to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The obscured feature detector further comprises a sensingcircuit coupled to the plurality of sensor plates, the sensing circuitbeing configured to measure the capacitance in the area surrounding eachof the sensor plates, a controller coupled to the sensing circuit, thecontroller being configured to receive the capacitance measurements fromthe sensing circuit, the controller configured to operate in a firstmode and a second mode, and the first mode configured to update theindicators at a first update frequency, and a second mode configured toupdate the indicators at a second update frequency. One or a pluralityof indicators are coupled to the controller, each indicator capable oftoggling between a deactivated state and an activated state, and thecontroller is configured to activate one or more of the indicators toidentify a location of an obscured feature.

The first update frequency may be ten indicator updates per second. Thefirst update frequency may be twenty indicator updates per second.Multiple capacitance readings from a single area may be combined todetermine a value of the measured reading pattern. The first mode maycombine more capacitance readings to determine a value of the measuredreading pattern, and the second mode may combine fewer capacitancereadings to determine a value of the measured reading pattern. The firstmode, or second mode, can be selected via an actuator. The controllermay select the mode of operation. The controller may automaticallyselect the mode. The controller may automatically select the mode afterthe capacitances have been measured.

In one embodiment, a method for determining the location of an obscuredfeature behind a surface comprises selecting a first mode or a secondmode of an obscured feature detector, the first mode being configured todetect obscured features of a predetermined depth behind the surface,and the second mode being configured to detect obscured features of apredetermined second depth behind the surface, placing the obscuredfeature detector on the surface, the obscured feature detector having aplurality of sensor plates arranged in an array, sensing the capacitancein an area surrounding one or more of the sensor plates, identifying,based upon the sensed capacitance, the location of one or a plurality ofobscured features, and activating one or a plurality of indicators topromote visual identification of the location of an obscured feature.

The step of selecting a mode may comprise selecting a deep scan mode.The step of selecting a mode may comprise selecting a shallow scan mode.A measured reading pattern may be defined by a set of measuredcapacitance values, and comparing, using the first mode, the measuredreading pattern with a plurality of predetermined patterns to identifythe predetermined pattern that best matches the measured readingpattern. One or more of the predetermined patterns may have capacitancevalues representing an obscured feature depth that is predetermined tobe deep or shallow.

In another embodiment, a method for determining the location of anobscured feature behind a surface comprises selecting a first mode or asecond mode of an obscured feature detector, the first mode beingconfigured update the indicators at a first update frequency, and thesecond mode being configured to update the indicators at a second updatefrequency, placing the obscured feature detector on the surface, theobscured feature detector having a plurality of sensor plates arrangedin an array, sensing the capacitance in an area surrounding one or moreof the sensor plates, identifying, based upon the sensed capacitance,the location of one or a plurality of obscured features, and activatingone or a plurality of indicators to promote visual identification of thelocation of an obscured feature.

In one embodiment, a method for determining the location of an obscuredfeature behind a surface comprises selecting a first mode or a secondmode, wherein the first mode has a first feature-detection threshold,and the second mode has a second feature-detection threshold, andplacing an obscured feature detector on the surface, the obscuredfeature detector having a plurality of sensor plates arranged in anarray. The method further comprises measuring capacitance readings in anarea surrounding one or more of the sensor plates, determining adisparity value defined by disparity in a set of measured capacitancereadings, determining, based upon a comparison of the disparity valueand the selected feature-detection threshold, whether an obscuredfeature is present, and activating one or a plurality of indicators toidentify the location of an obscured feature.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plates to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe sensor plates, the sensing circuit being configured to measure thecapacitance of each of the sensor plates, a controller coupled to thesensing circuit, the controller being configured to analyze thecapacitances measured by the sensing circuit, a surface materialdetection module coupled to the controller and configured to detect oneor more properties of a detected surface, and a correction modulecoupled to the controller and configured to apply corrections to themeasured capacitances using at least one of the properties detected bythe surface detection module.

The detected surface property may be, for example, the surface'sdielectric constant, or its thickness. The detected surface property maybe an estimation based on at least the surface's thickness anddielectric constant. The surface material detection module may use thesmallest measured capacitance from the plurality of capacitancesmeasured on the sensor plates to estimate a property of the surfacematerial. The surface material detection module may measure thecapacitance between two sensor plates to estimate a property of thesurface material. An estimate of a property of the surface may bemultiplied by a correction factor(s) to create an adjustment value(s);the adjustment value(s) may then be added to, or subtracted from, themeasured capacitance(s) to correct the capacitance reading(s). A firstcorrection factor may be applied to correct a capacitance measurementfrom a sensor plate that is near the edge of the detector, and a secondcorrection factor may be applied to correct a capacitance reading fromlocation sensor plate that is near the center of the detector. Theobscured feature detector may further comprise one or a plurality ofindicators coupled to the controller, each indicator may be capable oftoggling between a deactivated state and an activated state, and thecontroller may be configured to activate one or more of the indicatorsto identify a location of an obscured feature. The surface materialdetection module may compare capacitance readings that are derived fromtwo distinct plate activation patterns to estimate a property of thedetected surface. A pattern of plate activation configurations maycomprise a set of sensor plates that are floating.

In another embodiment, a method for determining the location of anobscured feature behind a surface comprises placing an obscured featuredetector on the surface, the obscured feature detector having aplurality of sensor plates arranged in an array, measuring capacitancereadings in an area surrounding one or more of the sensor plates,detecting at least one property of the surface, correcting thecapacitance readings, using the detected property of the surface, andidentifying, based upon the corrected capacitance readings, the locationof one or a plurality of obscured features. The method further comprisesthe step of activating one or a plurality of indicators to identify thelocation of an obscured feature.

The step of correcting the capacitance readings may use the surface'sdetected dielectric constant. The step of correcting the capacitancereadings may use the surface's detected thickness. The step ofcorrecting the capacitance readings may use a detected correction factorcomprising the surface's thickness and dielectric constant. Detecting aproperty of the surface may comprise using the one or more plates'smallest capacitance readings. Detecting a property of the surface maycomprise reading the capacitance between two sensor plates. Correctingthe capacitance readings may comprise multiplying the surface propertyby a correction factor, the product being an adjustment value, andadding or subtracting the adjustment value from the measuredcapacitances to correct the readings. Correcting the capacitancereadings may comprise applying a first correction factor to correct acapacitance reading from a location that is near the edge of thedetector, and applying a second correction factor to correct acapacitance reading from a location that is near the center of thedetector.

Detecting a surface property may comprise comparing readings from twodifferent plate activation patterns to create an estimate of a surfaceproperty. Detecting a surface property may comprise reading the sensorplates with a plate activation pattern comprising a set of sensor platesthat are read. Detecting a surface property may also comprise readingthe sensor plates with a plate activation pattern comprising a set ofsensor plates that are left floating.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plates to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled toat least two of the plurality of sensor plates, and the sensing circuitbeing configured to measure the aggregate capacitance of at least twocoupled sensor plates.

The obscured feature detector may further comprise a controller coupledto the sensing circuit, the controller may be configured to analyze thecapacitances measured by the sensing circuit, and one or a plurality ofindicators may coupled to the controller, each indicator capable oftoggling between a deactivated state and an activated state. Thecontroller may be configured to activate one or more of the indicatorsto identify a location of an obscured feature. The sensing circuit maybe configured to measure the aggregate capacitance of two adjacentsensor plates. The sensing circuit may be configured to measure theaggregate capacitance of two non-adjacent sensor plates. The obscuredfeature detector may comprise at least four sensor plates.

In another embodiment, a method of using an obscured feature detectorhaving a plurality of sensor plates to detect an obscured feature behinda surface comprises placing the obscured feature detector on thesurface, taking a capacitance reading of at least two of the pluralityof sensor plates, and transmitting said readings to a controller,identifying, based on the capacitance readings, a location of theobscured feature behind the surface, and activating one or moreindicators to indicate the location of the obscured feature behind thesurface.

Two adjacent sensor plates may be connected to thecapacitance-to-digital converter. Two non-adjacent sensor plates may beconnected to the capacitance-to-digital converter. The obscured featuredetector may comprise at least four sensor plates.

In one embodiment, an obscured feature detector comprises a plurality ofsensor plates, each having a capacitance that varies based on: (a) theproximity of the sensor plates to one or more surrounding objects, and(b) the dielectric constant(s) of the surrounding object(s). Theobscured feature detector further comprises a sensing circuit coupled tothe sensor plates, the sensing circuit configured to measure thecapacitance in the area surrounding each of the sensor plates, acontroller coupled to the sensing circuit, the controller configured toanalyze the capacitances measured by the sensing circuit, and one or aplurality of indicators coupled to the controller, each indicatorcapable of toggling between a deactivated state and an activated state.The controller is configured to detect a large obscured feature, whereinthe large obscured feature is approximately at least as large as thedetector, and to activate one or more of the indicators to identify alocation of a large obscured feature.

The controller may be configured to detect when the detector advancesover a large obscured feature, wherein the large obscured featuredetection initiates as the controller senses that an obscured feature isnear a group of adjacent of sensor plates, further wherein one of thesensor plates in the group of sensor plates is located at a leading endof the detector, and when the number of sensor plates in the group ofsensor plates is increasing. The controller may be configured torecognize a large obscured feature by first determining that most of thesensor plates are in front of an obscured feature, and then determiningthat all of the sensor plates have substantially the same readings. Thecontroller may be configured to activate all of the indicators when theentire detector is in front of an obscured feature that has a detecteddimension that is at least as wide as the length of the obscured featuredetector. The controller may be configured to activate all of theindicators when the entire detector is in front of an obscured featurethat is approximately the size of the detector or larger, when thedetector is placed over the obscured feature. The controller may beconfigured to determine that the detector is located in a region where alarge obscured feature is present if as the detector approaches a largeobscured feature all of the sensor plate readings have substantially thesame capacitance value. The sensor plate readings may be above athreshold value. The sensor plate readings may have a value that issubstantially similar to the value of the reading that detected anobscured feature when the detector was advancing over the large obscuredfeature.

In another embodiment, a method for determining the location of anobscured feature behind a surface comprises placing an obscured featuredetector on the surface, the obscured feature detector having aplurality of sensor plates arranged in an array, measuring capacitancereadings in an area surrounding one or more of the sensor plates,identifying, based upon the measured capacitance readings, when thedetector is over a large obscured feature, and activating one or aplurality of indicators to indicate the location of an obscured feature.

A first set of measured capacitive readings from a first time period anda second set of measured capacitive readings from a second time periodmay be used to identify when the detector is over an obscured feature. Afirst set of measured capacitive readings from a first time period and asecond set of measured capacitive readings from a second time period maybe used to identify when the detector is over an obscured feature andwherein when the capacitive readings from the second time period may besufficiently proximate to the capacitive readings from the first timeperiod then the controller identifies the region as one where anobscured feature is present. A first set of measured capacitive readingsfrom a first time period and a second set of measured capacitivereadings from a second time period may be used to identify when thedetector is over an obscured feature and wherein values from the firsttime period may be compared to the values from the second time periodonly if the controller identified the respective region as one where anobscured feature was present during the first time period. All of theindicators may be activated when the detector is over an obscuredfeature that is at least approximately as wide as the length of thedetector. A first set of measured capacitive readings from a first timeperiod and a second set of measured capacitive readings from a secondtime period may be used to identify when the detector is over anobscured feature, and wherein the detector may determine that thedetector may be near a large obscured feature in the first time period.A first set of measured capacitive readings from a first time period anda second set of measured capacitive readings from a second time periodmay be used to identify when the detector is over an obscured feature,and wherein the detector may determine that the detector may be near alarge obscured feature in the first time period, and wherein thedetector may determine that each of the measured capacitive readings aresubstantially similar in the second time period.

In another embodiment, an obscured feature detector comprises aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plates to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s). The obscured feature detector further comprises a multiplexerconnecting at least one of the sensor plates to a sensing circuit, andthe sensing circuit is configured to measure the capacitance of each ofthe sensor plates. A controller is coupled to the sensing circuit, thecontroller is configured to analyze the capacitances measured by thesensing circuit, and one or a plurality of indicators is coupled to thecontroller, each indicator capable of toggling between a deactivatedstate and an activated state. The controller is configured to activateone or more of the indicators to identify a location of an obscuredfeature.

The multiplexer may connect a single sensor plate to thecapacitance-to-digital converter. The multiplexer may connect more thanone sensor plate to the capacitance-to-digital converter. Themultiplexer may connect more than one non-adjacent sensor plate to thecapacitance-to-digital converter. The multiplexer may be configured sothat the sensing circuit measures the capacitance of one sensor plate.The multiplexer may be configured so that the sensing circuit measuresthe aggregate capacitance two or more sensor plates. The obscuredfeature detector may comprise at least four sensor plates.

In another embodiment, a method for determining the location of anobscured feature behind a surface comprises placing an obscured featuredetector on the surface, the obscured feature detector having aplurality of sensor plates arranged in an array, transmitting acapacitance reading from at least one of the sensor plates to acontroller, wherein the capacitance reading comprises the capacitance inan area surrounding the at least one sensor plate, and identifying,based upon the capacitance readings, the location of one or moreobscured features.

The method may further comprise activating one or more indicators toindicate the location of an obscured feature. The obscured featuredetector may comprise at least four sensor plates. Two adjacent sensorplates may be electrically connected to the sensing circuit. And twonon-adjacent sensor plates may be electrically connected to the sensingcircuit.

A novel and non-obvious feature of the obscured feature detector is theability to instantly identify the location of multiple objectssimultaneously.

A novel and non-obvious feature of the obscured feature detector is theability to identify the width of obscured features.

A novel and non-obvious feature of the obscured feature detector is theability to provide more reliable readings. The detector uses theinformation from multiple sensor plates' readings to determine thelocation of obscured features; as a result the detector is lesssusceptible to signal noise because more sensor readings are used todetermine the location of obscured features, making the detector lessdependent upon any single reading.

A novel and non-obvious feature of the obscured feature detector is theability to properly identify the location of features. In particular,other detectors may be less effective at properly identifying thepositions features, particularly when two features are relatively close.When two features are relatively close, the highest capacitive readingsmay be detected at the location that is between the two features, otherdetectors may incorrectly identify this as the location of an obscuredfeature. The obscured feature detector can properly identify thelocation of multiple features in close proximity.

A novel and non-obvious feature of the obscured feature detector is theability to create a detector that is easy to use. The user may only needto press a button and place it on a surface to identify the location ofobscured features. Prior art detectors tend to require more steps, andmore proficiency to determine the location of obscured features.

A novel and non-obvious feature of the obscured feature detector is theability more accurately detect obscured features through materials withinconsistent densities. Construction materials may have densityinconsistencies. Because the obscured feature detector has the abilityto use the information from multiple sensors to determine the locationof obscured features, errors in readings due to inconsistencies in thematerial have less effect on the detector's ability to identify thelocation of features.

A novel and non-obvious feature of the obscured feature detector is theability to detect features more deeply and to more accurately determinethe position of obscured features. The detector can combine informationfrom multiple sensor plates to determine the location of obscuredfeature(s). The use of more information provides higher qualityinterpretation of the detected features and may be able to detect moredeeply.

A novel and non-obvious feature of the surface-conforming obscuredfeature detector is the capability to create larger detectors.

The present disclosure will now be described more fully with referenceto the accompanying drawings, which are intended to be read inconjunction with both this summary, the detailed description, and anypreferred or particular embodiments specifically discussed or otherwisedisclosed. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to the embodiments setforth herein; rather, these embodiments are provided by way ofillustration only so that this disclosure will be thorough, and fullyconvey the full scope of the invention to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of an obscured feature detector thatis being used on one particular surface with two obscured features. Thetwo obscured features in this example are studs. In front of the studsthere is a surface material. On top of the surface material there is anobscured feature detector. In this example, the indicators that are infront of the obscured features are illuminated to indicate the locationsof the detected obscured features.

FIG. 2 is a perspective view of one embodiment of an obscured featuredetector.

FIG. 3 is a perspective view of one embodiment of an obscured featuredetector.

FIG. 4 is a block diagram that represents certain functional componentsof one embodiment of an obscured feature detector.

FIG. 5 is a block diagram of a controller suitable for use with anobscured feature detector.

FIG. 6 is a cross sectional view of an embodiment of an obscured featuredetector.

FIG. 7 illustrates a method of routing the several sensor plate traces,used in some embodiments. In this method all of the sensor plate traceshave the same length. All of the sensor plate traces are also uniformlyshielded on both sides. In FIG. 7 four sensor plates are alsoillustrated.

FIG. 8 is a flow diagram showing a feature detection process implementedin some embodiments of an obscured feature detector.

FIG. 9 is an illustration of a set of values that comprise an example ofone particular predetermined pattern. The “+” symbols represent thevalues of a predetermined pattern; larger values are higher on the page.In this example there is a surface and thirteen sensor plates. It is anexample of a predetermined pattern with a single stud. The “o” symbolsrepresent the location of indicators that may be activated if thispattern were selected as the best matching pattern.

FIG. 10 is an illustration of a set of values that comprise an exampleof one particular predetermined pattern. The “+” symbols represent thevalues of a predetermined pattern; larger values are higher on the page.In this example there is a surface and thirteen sensor plates. It is anexample of a predetermined pattern with two studs. The two studs areseparated by a distance of about two inches. The “o” symbols representthe location of indicators that may be activated if this pattern wereselected as the best matching pattern.

FIG. 11 is an illustration of a set of values that comprise an exampleof one particular predetermined pattern. The “+” symbols represent thevalues of a predetermined pattern; larger values are higher on the page.In this example there is a surface and thirteen sensor plates. It is anexample of a predetermined pattern with two studs. The two studs areseparated by a distance of about one half of an inch. The “o” symbolsrepresent the location of indicators that may be activated if thispattern were selected as the best matching pattern.

FIG. 12 is an illustration of a set of values that comprise an exampleof one particular predetermined pattern. The “+” symbols represent thevalues of a predetermined pattern; larger values are higher on the page.In this example there is a surface and thirteen sensor plates. It is anexample of a predetermined pattern with two studs. The two studs next toeach other. The “o” symbols represent the location of indicators thatmay be activated if this pattern were selected as the best matchingpattern.

FIG. 13 is an illustration of a surface and thirteen sensor plates. The“x” symbols represent the values of the readings; larger readings arehigher on the page. In FIG. 13 there are also four curves thatillustrate four different predetermined patterns.

FIG. 14 is a table showing an example of the calculation of the scoreusing a slope-based scoring method.

FIG. 15 is a table showing an example of the calculation of the scoreusing another slope-based scoring method.

FIG. 16 is a perspective view of one embodiment of an obscured featuredetector configured to detect large obscured features.

FIG. 17 is a perspective view of another embodiment of an obscuredfeature detector configured to detect large obscured features.

FIG. 18 is a perspective view of yet another embodiment of an obscuredfeature detector.

In the following description, reference is made to the accompanyingdrawings that form a part thereof, and in which is shown by way ofillustration specific exemplary embodiments in which the invention maybe practiced. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that modifications to the various disclosed embodimentsmay be made, and other embodiments may be utilized, without departingfrom the spirit and scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense.

DETAILED DESCRIPTION

To provide context for the disclosure it may be useful to understand howcapacitance is used to detect obscured features behind a surface.Capacitance is an electrical measure of an object's ability to hold orstore charge. A common form of an energy storage device is the parallelplate capacitor whose capacitance is calculated by: C=∈r ∈o A/d, where Ais the overlapping area of the parallel plates, d is the distancebetween the plates and ∈r is the relative static permittivity, ordielectric constant of the material between the plates, ∈o is aconstant. The dielectric constant (∈r) of air is one, while most solidnon-conductive materials have a dielectric constant greater than one.Generally, the increased dielectric constants of non-conductive solidsenable conventional capacitive displacement sensors to work.

In their most rudimentary form, capacitive sensors are in partsingle-plate capacitive sensors. These single-plate capacitive sensorsuse the environment surrounding them as the dielectric where the secondplate can be assumed to be infinitely far away. The plates will alsoform capacitors with other metal plates. When two plates are positionedagainst a wall, they are not facing each other as is suggested by thedefinition of a capacitor. Nonetheless, the stray fields emanating fromthe edges of each of the adjacent plates do extend into the wall andbehind it, and curve back to an adjacent plate, forming a capacitor.

When the plates are placed on a wall at a location with no supportbehind the wall, the detector 10 measures the capacitance of the walland the air behind it. When placed in a position having a support behindthe wall, the detector 10 then measures the capacitance of the wall andthe support, which has a higher dielectric constant than air. As aconsequence, the detector 10 registers an increase in capacitance whichcan then be used to trigger an indicating system.

This description of feature sensing through capacitive sensing isprovided in order to facilitate an understanding of the disclosure.Persons of skill in the art will appreciate that the scope and nature ofthe disclosure is not limited by the description provided.

The present disclosure is directed to an obscured feature detector 10.In the exemplary embodiments illustrated in FIGS. 1, 2, 3, 4, and 6 theobscured feature detector 10 comprises a sensor plate array 31 (see FIG.7), a multi-layer printed circuit board 40 (see FIGS. 2, 3, and 6), asensing circuit 30 (see FIG. 4), a controller 60 (see FIGS. 4, 5), adisplay circuit 50 (see FIG. 4), a plurality of indicators 52 (see FIGS.1, 3, 4, and 6), a power controller 20 (see FIG. 4), and a housing 12(see FIGS. 1, 2, 3, and 6).

In some embodiments, as shown in FIG. 7, the sensor plate array 31comprises two or more sensor plates 32 arranged substantially in aplane. Each sensor plate 32 has a capacitance that varies based on: (a)the proximity of the sensor plate 32 to one or more surrounding objects,and (b) the dielectric constant(s) of the surrounding object(s). Thus,by evaluating the capacitances of the sensor plates 32, the sensor platearray 31 is capable of sensing the presence and location of one or morefeatures obscured by a surface (see FIG. 1) in contact or proximity withthe obscured feature detector 10. In some embodiments each of the sensorplates 32 are substantially the same size.

The sensor plates 32 can be positioned side by side in a lineararrangement so that a longitudinal axis of the array 31 is substantiallyperpendicular to a longitudinal axis of the individual sensor plates 32.In some embodiments, the obscured feature detector 10 comprises thirteensensor plates 32, with a gap of approximately 1.7 mm between adjacentplates. In some embodiments, each sensor plate 32 has a width of about11 mm wide and a length of about 47 mm. The individual plates 32 cancomprise thin, conductive surfaces and can be manufactured using avariety of suitable techniques, such as, for example, depositingconductive ink on a substrate or applying thin sheets of conductivematerial to the substrate.

In some embodiments, each individual sensor plate 32 of the sensor platearray 31 can be independently connected to the capacitance-to-digitalconverter 38 via a multiplexer 37 (see FIG. 4), and the sensor platearray 31 itself is attached to a layer 41 of the printed circuit board40, the printed circuit board 40 being positioned on the underside ofthe detector 10 (see FIG. 6). In some embodiments, the obscured featuredetector 10 has at least four sensor plates 32, which advantageouslyenables the obscured feature detector 10 to detect the full width of acommon obscured feature, such as a stud 95, from a stationary position.By contrast, many existing stud detectors with fewer than four sensorplates 32 cannot detect the full width of a stud 95 without being moved.

In some embodiments, as shown in FIG. 6, the printed circuit board 40comprises a multi-layer board with a layer comprising a sensor board 41on which the sensor plate array 31 and other electrical traces areplaced, one layer comprising a ground plane board 43 upon which a groundplane and other electrical traces are placed, a power plane board 42upon which a power plane and other electrical traces are placed, and atop layer comprising a metal shielding 44, and other electrical traces.In some embodiments the sensor plate array 31 is placed on an internallayer of the printed circuit board 40 which may protect the circuitsfrom some electrostatic discharge. Placing the sensor plates 32 on aninternal layer may also minimize the expansions and contractions of thesensor plates 32 as the printed circuit board 40 is flexed. Sensorplates 32 that do not expand and contract with flexing may provide moreconsistent readings. In some embodiments the electrical traces compriseelectrically conductive paths.

The printed circuit board 40 can be made from a variety of suitablematerials, such as, for example, FR-4, FR-406, or more advancedmaterials used in radio frequency circuits, such as Rogers 4003C. Rogers4003C, and other radio-frequency-class printed circuit board substrates,may offer improved performance across a broader temperature range. Inthe embodiment illustrated in FIG. 6, the printed circuit board 40 ispositioned external to the housing 12.

In some embodiments, as shown in FIG. 4, the sensing circuit 30comprises a plurality of sensor a voltage regulator 26, and acapacitance-to-digital converter 38. The sensing circuit 30 can beconnected to the controller 60. The sensor plate traces 35 can compriseelectrically conductive paths on the printed circuit board 40, which mayconnect the individual sensor plates 32 to the capacitance-to-digitalconverter 38, the connection being made via the multiplexer 37. Themultiplexer 37 can individually connect the sensor plates 32 to thecapacitance-to-digital converter 38.

In some embodiments the multiplexer 37 may connect and single sensorplate 32 to the sensing circuit. In some embodiments, the multiplexer 37may connect more than one adjacent sensor plates 32 to the sensingcircuit. In some embodiments, the multiplexer 37 may connect more thanone non-adjacent sensor plates 32 to the sensing circuit. In someembodiments, the multiplexer 37 is configured so that the sensingcircuit measures the capacitance of one sensor plate 32. In someembodiments, the multiplexer 37 is configured so that the sensingcircuit measures the aggregate capacitance two or more sensor plates 32.

As used herein, the term “module” can describe any given unit offunctionality that can perform in accordance with one or moreembodiments of the present invention. For example, a module might byimplemented using any form of hardware, software, or a combinationthereof, such as, for example, one or more processors, controllers 60,ASICs, PLAs, logical components, software routines, or other mechanisms.

In some embodiments, as shown in FIG. 5, the controller 60 comprises aprocessor 61, a clock 62, a random access memory (RAM) 64, and anon-volatile memory 65. In operation, the controller 60 receives programcode 66 and synchronizes the functions of the capacitance-to-digitalconverter 38 and the display circuit 50 (see FIG. 4). The non-volatilememory 65 receives and holds the programmable code 66 as well as look-uptables (LUT) and calibration tables 68. The program code 66 can includea number of suitable algorithms, such as, for example, an initializationalgorithm, a calibration algorithm, a pattern-matching algorithm, amultiplexing algorithm, a display management algorithm, an active sensoractivation algorithm, and a non-active sensor management algorithm.

The capacitance-to-digital conversion process can be accomplished by theAD7147 from Analog Devices. Other integrated circuits that can be usedto perform the capacitance-to-digital conversion include the AD7477 fromAnalog Devices, the CY8C21534 from Cypress Semiconductor, the C8051CF706from Silicon Laboratories, or others. The voltage regulator 26 maycomprise the ADP150-2.8 from Analog Devices which provides very lownoise. The controller 60 may comprise the C8051F543 from SiliconLaboratories, or any of many other microcontrollers.

In some embodiments, as shown in FIGS. 2, 3, and 6 the housing 12comprises an upper housing 13, an on/off switch 24, a handle 15, aplurality of light pipes 18, and a power supply compartment 16. In someembodiments the underside of the housing 12 is attached to a first sideof a foam ring 70. In some embodiments the foam ring 70 is made ofnon-conductive EPDM foam rubber. In some embodiments the foam ring 70 isattached to the housing 12 using a pressure sensitive acrylic adhesive.In some embodiments the foam ring 70 is attached to the printed circuitboard 40 using a pressure sensitive acrylic adhesive. In someembodiments the multi-layered printed circuit board 40, contains thecapacitance-to-digital converter 38, the display circuit 50, and thecontroller 60. In some embodiments, the upper housing 12 comprisesplastic. In some embodiments, the upper housing 12 comprises ABSplastic.

In some embodiments, the handle 15 comprises a gripping surface. In someembodiments a portion of the gripping surface comprises an elastomer. Insome embodiments the gripping surface is positioned such that when thedetector 10 is held on a wall in a position to detect a verticalfeature, such as a vertical stud 95, the handle 15 is substantiallyhorizontal or substantially perpendicular to the vertical stud 95. Insome embodiments the gripping surface that is oriented such that whenthe detector 10 is held on a wall in a position to detect vertical studs95, two or more fingers are lined up with an orientation that is morehorizontal than vertical. In some embodiments the gripping surface is acurved surface. In some embodiment the gripping surface is asubstantially flat surface.

The handle 15 is preferably positioned so that the user's hand does notobscure the view of the indicators 52 when grasping the handle 15. Insome embodiments, the power supply compartment 16 comprises a cavity forholding a suitable power supply, such as batteries, and a cover foraccessing the compartment 16.

In order to accommodate the thirteen sensor plates 32, the housing 12can have a length of about seven inches and a width of about threeinches. A handle 15 running along the longitudinal axis of the upperhousing 13 can be designed to be easy to hold while keeping the user'shand about one inch away from the surface of the PCB 40 and at the sametime not obscuring the user's line of sight to the rows of indicators 52positioned on the back side of the upper housing 13. In some embodimentsthe indicators 52 are LEDs (Light Emitting Diodes). In otherembodiments, the user's hand may be less than one inch away from thesurface of the printed circuit board 40

In some embodiments, as shown in FIG. 4, the obscured feature detector10 comprises a power controller 20 having a power source 22, an on-offswitch 24, and a voltage regulator 26. The power source 22 can comprisean energy source for powering the indicators 52, and supplying power tothe capacitance-to-digital converter, and the controller 60. In someembodiments, the power source 22 can comprise a DC battery supply. Theon-off switch 24 can be used to activate controller 60 and othercomponents of the obscured feature detector 10. In some embodiments, theon-off switch 24 comprises a push button mechanism that activatescomponents of the obscured feature detector 10 for a selected timeperiod. In some embodiments the push button activates the componentssuch that the components remain activated until the button is released.In some embodiments the on-off switch 24 comprises a capacitive sensorthat can sense the presence of a finger, or thumb over the button. Insome embodiments, the on-off switch 24 can comprise a toggle switch, orother types of buttons or switches. The voltage regulator 26 may be usedto condition the output of the power controller 20, as desired. In someembodiments a voltage regulator 26 is placed as near as possible to thecapacitance-to-digital converter 38, which may provide a better powersource 22 to the capacitance-to-digital converter 38.

Different processes of reading a capacitance and converting it to adigital value, also known as a capacitance-to-digital conversion, arewell-described in the prior art. The many different methods are notdescribed here, the reader is referred to the prior art for detailsabout different capacitance-to-digital converter methods. Someembodiments use a sigma-delta capacitance-to-digital converter 38, suchas the one that is built into the Analog Devices AD7147 integratedcircuit. Some embodiments use a charge-sharing method ofcapacitance-to-digital conversion.

FIG. 8 is a flow diagram showing a feature detection process 200implemented in some embodiments of the obscured feature detector 10. Thedetection process 200 begins with a first step 202, in which theobscured feature detector 10 is initialized. In some embodiments,initialization occurs automatically after the obscured feature detector10 is turned on. Upon initialization, some embodiments immediatelyperform a set of capacitance-to-digital conversions to “warm-up” thecircuitry. Next the sensor plates 32 are read.

Detecting obscured features can require a high degree of accuracy, andmay require more accuracy than a capacitance-to-digital converter 38 mayable to provide, if the native capacitance-to-digital converter readingsare used alone. Native readings are the raw values read from thecapacitance-to-digital converter 38, they are the digital output of thecapacitance-to-digital converter 38.

Some embodiments perform native reads multiple times, and combine theresults of the multiple native reads, to create a reading. Someembodiments perform native reads multiple times, and combine the resultsof the multiple native reads, using a different configuration for two ormore of the native reads to create a reading. Some embodiments performnative reads multiple times, and sum or average the results of themultiple native reads, to create a reading. In some embodiments thisimproves the signal to noise ratio. Each native read may involve readingone sensor plate 32. A native read could also involve reading aplurality of sensor plates 32, if multiple sensor plates 32 aremultiplexed to the capacitance-to-digital converter 38. In the someembodiments multiple native reads are combined to create a reading.

Summing or averaging multiple native reads may improve the signal tonoise ratio, but it may not reduce the effect of non-linearities in thecapacitance-to-digital converter 38. An ideal capacitance-to-digitalconverter 38 is perfectly linear, which means that its native readingsincrease in direct proportion to an increase in the capacitance beingsensed. However, many capacitance-to-digital converters 38 may not becompletely linear, such that a change in the input capacitance doesn'tresult in an exactly proportional increase in the native reading. Thesenon-linearities may be small, but when a high degree of accuracy isdesired it may be desirable to implement methods that reduce the effectsof the non-linearities.

In some embodiments, the ill effects of the non-linearities may bemitigated by summing multiple native reads, using a slightly differentconfiguration for each of the native reads. Some embodiments performnative reads using two or more different configurations. For example,the AD7147 from Analog Devices has a capacitance-to-digital converter38, which may be used by some embodiments. The AD7147 offers a fewdifferent parameters that can be set in different ways to createdifferent configurations.

For example, with the AD7147, the bias current is one of the parametersthat can be altered to create different configurations. The bias currentcould be set to normal, or normal +20%, or normal +35%, or normal +50%.Different bias currents produce different native readings, even if allother factors remain constant. Since each native reading has a differentvalue, presumably each native reading may be subject to differentnon-linearities. Presumably summing or averaging readings that aresubject to different non-linearities may cause the non-linearities topartially cancel each other out, instead of being summed, or multiplied.

The AD7147 chip also has two separate and independentcapacitance-to-digital converters 38. Presumably each of them may havedifferent non-linearities. By using both of the capacitance-to-digitalconverters 38, using a first converter for some of the reads, and usingthe second converter for some of the reads, may mitigate the effect ofany single non-linearity.

The AD7147 capacitance-to-digital converter 38 also offers adifferential connection to the capacitance-to-digital converter 38, or asingle ended connection to the capacitance-to-digital converter 38. Bothconnections can be used for single ended reads, but each connectionmethod provides results with different values. Doing some reads with afirst capacitance-to-digital converter 38, and some reads with a secondcapacitance-to-digital converter 38, and summing the results, maymitigate the effect of any single non-linearity.

Some embodiments perform native reads on each of thirteen sensor plates32 using each of twelve different configurations. Therefore, to readeach of thirteen sensor plates 32 twelve times each requires one hundredand fifty six native reads. Other embodiments may use other parametersto created different configurations.

After completing the readings, in some embodiments, two differentcalibration algorithms may be performed: first an individual-platecalibration that adjusts for individual sensor plate 32 variations, andsecond a surface material calibration that adjusts the readings so thatthey are tuned to the surface density/thickness. Other embodiments mayonly use one of the two calibration algorithms. Some embodiments may useother calibration algorithms. In some embodiments the calibrationalgorithms are performed by a calibration module.

In some embodiments, individual plate calibration is employed first.With individual plate calibration, each sensor may have its ownindividual calibration value. In some embodiments, after the readingsare taken, an individual plate calibration value is added to, orsubtracted from, each of the readings. Other embodiments may usemultiplication, or division, or other mathematical functions to performthe individual plate calibration. In some embodiments, the individualplate calibration value is stored in non-volatile memory. Individualplate calibration compensates for individual sensor plate 32irregularities, and is used to compensate for these irregularities. Itis presumed that after performing individual plate calibration that thereadings will presumably have the same calibrated values, if the sensorplate readings are taken while the detector 10 is on a surface that issimilar to the surface the detector 10 was calibrated with. For example,if readings are performed on ½″ sheetrock 80, without any obscuredfeatures present, and the individual calibration values were created for½″ sheetrock 80, then after performing individual plate calibration, itis presumed that all the readings would be corrected to a common value.If readings are performed on a thicker material (such as ⅝″ sheetrock80), or thinner material (such as ⅜″ sheetrock 80), or a differentmaterial (such as ¾″ plywood) then there may be some error in thevalues. Surface material calibration may help correct this error.

In some embodiments surface material calibration may be used in partbecause the sensor plates 32 near the center of the detector 10 may havecapacitive coupling with adjacent sensor plates 32 on both sides,whereas sensor plates 32 near the end of the detector 10 may only havecapacitive coupling with adjacent sensor plates 32 on one side. Thevalue of these capacitors may differ, depending on the thickness anddensity of the surface material. In some embodiments the sensor plates32 near the ends of the detector 10 may be more sensitive to thethickness and density of the material being tested than the plates nearthe center.

To better explain this phenomenon by way of example, suppose that thedetector 10 is placed on a sheet of ½″ sheetrock 80 without any obscuredfeatures present and the detector 10 is calibrated such that all of thereadings are adjusted such that they all read a common value, such as 0.Next the detector 10 is placed on the surface of another material thatis has a higher dielectric constant, such as ½″ MDF (medium densityfiberboard). The readings from the sensor plates 32 that are near centerof the detector may now read a value of 80, while the readings from thesensor plates 32 that are near the edge of the detector 10 may now reada value of 110. Thicker and denser materials may cause more change toreadings from sensor plates 32 near the edge of the detector than toreadings from sensor plates 32 near the center of the detector.

To compensate, some embodiments use a surface material estimationmodule, so that compensation can be made to minimize this effect. Thesurface material estimation module estimates a property that can be usedto correct this error. The surface material estimation module mayestimate a property of the surface material. In some embodiments ahigher property value coincides with a material has a greater effect onthe pads near the edges, than on the pads near the center. The surfacematerial property in some embodiments is a one value parameter; highervalues may correspond to a thicker and denser surface. Some embodimentsmay use multiple properties to estimate properties of the surfacematerial.

In some embodiments, the dielectric constant of the surface is aproperty of the surface that is estimated by the surface materialdetection module. In some embodiments, the thickness of the surface is aproperty of the surface that is estimated by the surface materialdetection module. In some embodiments, the property of the surface thatis estimated is a factor that is comprised of a combination of thethickness of the surface material, and dielectric constant of thesurface material. In some embodiments the surface detection module usesthe smallest measured capacitance to estimate a property of the surfacematerial.

Presumably, the smallest measured capacitance reading may correspond toa surface that does not have an obscured feature behind it. The smallestmeasured capacitance reading may provide a good estimate of surfacematerial property. In some embodiments, where the detector 10 is onlyintended for one type of material (such as only sheetrock 80) this maybe sufficient.

In some embodiments, a surface material property can be estimated bycreating a dual-plate capacitor between adjacent sensor plates 32 andreading the value of the capacitor. This may be accomplished in someembodiments by reading the value of a sensor plate 32, while one or bothof the adjacent sensor plates 32 are grounded.

In some embodiments two different patterns of plate activationconfigurations are compared to create an estimate of a property of asurface. In some embodiments a pattern of plate activationconfigurations comprises a set of sensor plates 32 that are read. Insome embodiments a pattern of plate activation configurations comprisesa set of sensor plates 32 that are floating. In some embodiments apattern of plate activation configurations comprises a set of sensorplates 32 that are driven at a constant voltage. In some embodiments apattern of plate activation configurations comprises a set of sensorplates 32 that are driven as active shields. Active shields are drivenwith a voltage that is similar to the voltage that is driven on thesensor plates 32 that are being read. In some embodiments a pattern ofplate activations configurations comprises a set of sensor plates 32that are read, and a set of sensor plates 32 that are floating.

In some embodiments, including the embodiments that use the AnalogDevices AD7147 integrated circuit, each of the individual sensor plates32 can be activated in any of at least three different ways (1) asactively driven plates that are being read—designated with a “R”, (2)plates driven as active shields—designated with a “S” (these plates aredriven with a voltage that is similar to the voltage being driven on theplate that is being read), and (3) plates that are leftfloating—designated with an “F”. Many different sensor plate 32configurations are possible. For example, SSSSSSRSSSSSSS implies thatthe first 6 plates are driven as active shields, the center plate is adriven and read plate, and then the final 6 plates are driven as activeshields. By comparing readings between two different configurations ofplates, a property of the surface material can be estimated. There aremany different configurations of plates that can be tested such asFFFFFFRFFFFFF, FFFRSSRFFFF, FFFFFRSRFFFFF, FFFFFFRSSSSSS, SSSSSSRFFFFFF,FFFFRSSRFFF, SSSRFFRSSSS, SSSSSRRFFFFFF, FFFFRFRFRFFFF, and many others.Those skilled in the art can select the configurations that are mostsuitable for their application. Testing the different configurations maybe the most effective means of selecting the configurations that may bemost effective in a particular application. In some embodimentscomparing readings from the pattern FFFRFRFRFRFFF to patternSSSRSRSRSRSSS may be effective at estimating a surface materialproperty. In some embodiments comparing readings from the patternSSSSSFRFSSSSS to pattern SSSSSSRSSSSSS may be effective at estimating asurface material property. In some embodiments comparing readings fromthe pattern FFFRFFRFFRFFF to pattern SSSRSSRSSRSSS may be effective atestimating a surface material property. In some embodiments more thanone estimation procedure is used. Those skilled with mathematics canselect the patterns, or combinations of patterns that are most usefulfor correcting for the desired surfaces.

Some embodiments do not perform surface material calibration. Forexample, some embodiments that are only designed to operate on one typeof surface may not perform surface material calibration.

In some embodiments, after a surface material property is estimated, thereadings are adjusted. In some embodiments an estimate of a property ofthe surface is multiplied by a correction factor(s) to create anadjustment value(s), the adjustment value(s) is then added to, orsubtracted from, the measured capacitance(s) to correct the capacitancereading(s). In some embodiments a first correction factor is applied tocorrect a capacitance reading from a location that is near the edge ofthe detector, and a second correction factor is applied to correct acapacitance reading from a location that is near the center of thedetector.

In some embodiments the correction factor(s) comprise a predeterminedset of values that are stored in a non-volatile memory. Thepredetermined set of values can be scaled, where the scaling factor isthe surface material property. In some embodiments the scaled set ofvalues can then be added to, or subtracted from, the readings. Otherembodiments may use calibration adjustments that comprisemultiplication, or division, or other mathematical functions.

In some embodiments, after calibrating the sensor plate readings thedetector 10 decides if an obscured feature is present. In someembodiments the lowest sensor plate reading is subtracted from thehighest sensor plate reading. If the difference is greater than athreshold value then a determination is made that an obscured feature ispresent. See FIG. 8.

If it is determined that no obscured features are present, then all ofthe indicators 52 may be deactivated. If an obscured feature is presentthen the detector 10 begins the process of determining the position(s)and width(s) of the obscured feature(s).

In some embodiments, the next step is to scale the all of the currentsensor plate readings such that the lowest reading is scaled to apredetermined value (such as 0) and the maximum reading is scaled to asecond predetermined value (such as 100). All intermediate values may bescaled proportionately. Scaling the readings may make it easier tocompare the readings to a set of predetermined patterns.

In some embodiments a pattern matching module is used to determine thelocation of obscured features. The pattern matching module compares thecalibrated and scaled readings from the sensor plates 32 topredetermined patterns to identify the pattern that best matches sensorplate readings. The calibrated and scaled readings may also be referredto as current readings, or simply readings. A set of calibrated andscaled readings may be referred to as a measured reading pattern.

In some embodiments the pattern matching module uses a measured readingpattern as an input. In some embodiments, the measured reading patternis comprised of the group of the current sensor plate readings that havebeen calibrated and scaled. The pattern matching module uses a pluralityof predetermined patterns, each predetermined pattern comprising a setof predetermined values. The module compares the reading pattern to eachof the predetermined patterns. Then the pattern matching moduledetermines which predetermined pattern most closely matches the readingpattern. After the closest-matching pattern is determined, the locationof one or more obscured features can be identified. In some embodiments,the set of predetermined patterns may consist of, for example, a patternthat is consistent with the detector performing a reading on surface ofsheetrock 80 with a single stud 95 behind the sheetrock 80. The set ofpredetermined patterns may include multiple patterns corresponding to asingle stud 95, where each pattern corresponds to a single stud 95 in adifferent location. Another predetermined pattern may be consistent withthe detector performing a reading on a surface of sheetrock 80 with twostuds 95 behind the sheetrock 80, the two studs 95 separated by abouttwo inches. In some embodiments, the set of predetermined patterns mayinclude predetermined patterns that correspond to three obscuredfeatures, so that it may be possible to detect three or more featuressimultaneously. In some embodiments, the set of predetermined patternsmay include predetermined patterns that correspond to features withdifferent widths, which may enable the detector to identify the width ofan obscured feature. Many different patterns can be created,corresponding to different sizes of obscured features, differentlocations of obscured features, different numbers of obscured features,or obscured features with different material compositions. In someembodiments approximately one hundred and fifty predetermined patternsmay be used. In some embodiments approximately one hundred and fiftyunique predetermined patterns may be used. In some embodiments thenumber of predetermined patterns is at least 30 unique patterns. In someembodiments the predetermined patterns may correspond to obscuredfeatures that are studs 95. In some embodiments the predeterminedpatterns may correspond to other obscured features such as pipes, wires,rebar, conduit, beams, metal studs, 50 and 60 Hz electric fields, orother obscured features.

FIGS. 9, 10, 11, and 12 illustrate embodiments with thirteen sensorplates 32. Each of the figures shows the thirteen sensor plates 32 and asurface. The “+” symbols in each of the figures represent the valuesthat comprise a predetermined pattern. In some embodiments, each of thepredetermined patterns is comprised of thirteen values. For example inFIG. 9 there are thirteen “+” symbols which correspond to the thirteenvalues which comprise a predetermined pattern. In this particularexample, each of the sensor plates 32 corresponds to one value in apredetermined pattern. In some embodiments there is one value in thepredetermined pattern for each sensor plate 32. In some embodimentsthere may be more values in the predetermined pattern than there aresensor plates 32. In some embodiments there may be fewer values in thepredetermined pattern than there are sensor plates 32. FIG. 9illustrates the values of a predetermined pattern for a surface with asingle stud 95 behind it. FIG. 10 illustrates the values of apredetermined pattern for a surface with two studs 95 behind it, the twostuds 95 being spaced about two inches apart. FIG. 11 illustrates thevalues of a predetermined pattern for a surface with two studs 95 behindit, the two studs 95 being about one half inch apart. FIG. 12illustrates the values of a predetermined pattern for a surface with twostuds 95 behind it, the two studs 95 being next to each other. In eachof the examples in FIGS. 9, 10, 11, and 12 the letter “o” represents theindicators 52 that may be associated with each of the patterns. Theletter “o” in FIGS. 9, 10, 11, and 12 represents the indicators 52 thatmay be activated if each respective pattern were to be selected as thebest matching predetermined pattern. FIGS. 9, 10, 11, and 12 show fourrepresentative predetermined patterns, corresponding to each of fourdifferent combinations of obscured features. Many more than fourpredetermined patterns may be used in some embodiments. In someembodiments there is one indicator 52 that is associated with eachsensor plate 32. Other embodiments may have more, or fewer, indicators52 than sensor plates 32.

FIG. 13 illustrates the measured reading patterns, as represented by thesymbol “x”. Superimposed on the image are representations of the fourdifferent predetermined patterns from FIGS. 9, 10, 11, and 12. Thepattern matching module selects the best matching pattern, and activatesthe indicators 52 associated with the best matching pattern.

In some embodiments the set of predetermined patterns can be determinedin advance by physically testing each configuration using an actualsurface material, such as sheetrock 80, and an actual obscuredfeature(s), such as stud(s) 95, then storing the results of the readingsas the pattern for each respective configuration.

In some embodiments a single pattern may be determined by physicallytesting a particular configuration with an actual surface and an actualobscured feature, and then other patterns may be derived from the testedpattern. For example a predetermined pattern could be determined byreading the sensor plates 32 through a surface, with an obscuredfeature, such as a stud 95 on the opposite side. Then, the otherpatterns could be derived from this single-feature pattern. For example,the values for other patterns that involve a single stud 95 could becreated by shifting the one tested pattern to other positions.

In some embodiments dual-feature patterns are derived from twosingle-feature patterns. In some embodiments two single-feature patternscan be added together to create the pattern that represents aconfiguration with two obscured features.

In some embodiments the complete set of predetermined patterns arestored in non-volatile memory at the factory. In some embodiments theset of predetermined patterns are calculated from the single-featurepattern by the program and stored in memory each time the detector 10 isinitialized. In some embodiments the predetermined patterns arecalculated and stored in ROM (read-only memory) when a calibrationroutine in executed. In some embodiments each predetermined pattern iscalculated in real-time, just before it is needed.

In some embodiments each of the predetermined patterns are scaled suchthat the lowest value in the pattern is zero and the highest value inthe pattern is one hundred. Likewise in some embodiments the readingpattern is scaled such that the lowest value in the pattern is set tozero and the highest value in the pattern is scaled to one hundred. Insome embodiments the patterns and readings are scaled such that thehighest value is 255, corresponding to the maximum number that can fitin a single computer byte.

In some embodiments the reading pattern is compared to each of thepredetermined patterns and a score is given to each comparison. Thescore represents the amount of similarity between the reading patternand the predetermined pattern. A lower score represents more similaritybetween the reading pattern and the respective predetermined pattern. Insome embodiments the score is determined by comparing each value of thereading pattern to each value of the respective predetermined pattern.The following formula is used by some embodiments to create a scorebased upon a comparison of the reading pattern values, to thepredetermined pattern values.

Score (based upon value comparisons)=|R1−Px_1|+|R2−Px_1+|R3−Px_3|+ . . .+|R3−Px_12|

The reading pattern is given by the set of values R0, R1, R2, . . . ,R12, for sensor plate0 thru sensor plate12 respectively, where each ofthe values R0, R1, R2, . . . , R12 are calibrated and scaled readingswhere the minimum value is zero and the maximum value within the patternis scaled to one hundred.

The predetermined pattern for Pattern0 is given by P0_0, P0_1, P0_2, . .. , P0_12.

The predetermined pattern for Pattern1 is given by P1_0, P1_1, P1_2, . .. , P1_12.

The predetermined pattern for Pattern151 is given by P151_0, P151_1,P151_2, . . . , P151_12.

Each of the predetermined patterns consists of calibrated and scaledvalues where the minimum value within the pattern is zero and themaximum value within the pattern is scaled to one hundred.

In some embodiments a score is calculated by comparing the slope ofvarious segments of the reading pattern to the slope of various segmentsof each predetermined pattern.

In some embodiments slope segments are based upon slopes that arecreated by comparing readings from plates that are one sensor plate 32apart. In some embodiments slope segments are based upon slopes that arecreated by comparing readings that are adjacent, adjacent readings thatare one apart. Some embodiments use the following formula.

Score Based on Slope, Using a Slope That is Calculated by ComparingReadings From Plates that are One Sensor PlateApart=|(R1−R0)−(Px_1−Px_0)|+|(R2−R1)−(Px_2−Px_1)|+|(R3−R2)−(Px_3−Px_2)|+. . . +|(R12−R11)−(Px_12−Px_11)|

Table 1 in FIG. 14 shows an example of the calculation of the scoreusing this scoring method. In this example two predetermined patterns,Predetermined Pattern A and Predetermined Pattern B are compared to theMeasured Reading Pattern. The absolute values of the differences betweenthe Measured Reading Pattern values and each of the values of thePredetermined Pattern are calculated, and scores are calculated. A lowerscore identifies a closer match between the Measured Reading Pattern andthe respective predetermined pattern.

In some embodiments slope segments are based upon slopes that arecreated by comparing readings from sensor plates 32 that are two sensorplates 32 apart. In some embodiments slope segments are based uponslopes that are created by comparing readings that are two apart. Someembodiments use the following formula.

Score Based on Slope, Using a Slope That is Calculated by ComparingReadings From Plates that are Two Sensor Plates Apart=|(R2−R0)−(Px⁻2−Px_0)|+|(R3−R1)−(Px⁻ 3−Px_1)|+|(R4−R2)−(Px_4−Px_2)|+ . . .+|(R12−R10)−(Px_12−Px_10)|

Table 2 in FIG. 15 shows an example of the calculation of the scoreusing this scoring method. In this example two predetermined patterns,Predetermined Pattern A and Predetermined Pattern B are compared to theMeasured Reading Pattern. Slopes between values of the predeterminedpatterns are calculated. The absolute values of the differences betweenthe slopes are calculated. A lower score identifies a closer matchbetween the Measured Reading Pattern and the respective predeterminedpattern.

In some embodiments plates slopes segments are based upon slopes thatare created by comparing readings from plates that are three sensorplates 32 apart. In some embodiments slope segments are based uponslopes that are created by comparing readings that are three apart. Someembodiments use the following formula.

Score Based on Slope, Using a Slope That is Calculated by ComparingReadings From Plates that are Three Sensor PlatesApart=|(R3−R0)−(Px_3−Px_0)|+|(R4−R1)−(Px⁻ 4−Px_1)|+|(R4−R2)−(Px⁻4−Px_2)|+ . . . +|(R12−R10)−(Px_12−Px_10)|

Some embodiments use a combination of multiple scoring formulas. Someembodiments use the score based upon value comparisons to help determinethe best matching pattern. Some embodiments use score based on slope,using a slope that is calculated by comparing readings from plates thatare one sensor plate 32 apart to help determine the best matchingpattern. Some embodiments use score based on slope, using a slope thatis calculated by comparing readings from plates that are two sensorplates 32 apart to help determine the best matching pattern. Someembodiments use score based on slope, using a slope that is calculatedby comparing readings from plates that are three sensor plates 32 apartto help determine the best matching pattern. Some embodiments determinethe score by using the sum of the results of the four differentdescribed scoring schemes: score based upon value comparisons, scorebased upon slope comparisons from plates that are one plate apart, scorebased upon slope comparisons from plates that are two plates apart,score based upon slope comparisons from plates that are three platesapart. Many different scoring methods are possible.

In some embodiments the lowest score is selected as the best-matchingpattern. In some embodiments each predetermined pattern has a set ofindicators 52 that are associated with it. In some embodiments theindicators 52 that are associated with the best matching pattern areactivated. In some embodiments one or more of the predetermined patternshas indicator(s) 52 associated with the predetermined patterns thatcorrespond to a set of indicators 52 that spans about one and one halfinches. This may be used, for example, to indicate the location of astud 95. In some embodiments, one more of the predetermined patternshave indicator(s) 52 associated with the predetermined patterns thatcorrespond to the edges of an obscured feature. This may be used in someembodiments to indicate the edges of an obscured feature.

In some embodiments, different combinations of read configurations arecombined. For example, in some embodiments, the second sensor plate 32is sensed individually, followed by the first, second and third sensorplates 32 being grouped together and sensed as a unit. These tworeadings may then combined by the detector 10 to create a reading. Manycombinations are possible.

In some embodiments, differential detection is employed, whereby onegroup of sensor plates 32 is compared to an alternate group of sensorplates 32. The groups of compared sensor plates 32 may, or may not, beadjacent. Each group of compared sensor plates 32 can comprise one ormore sensor plates 32. Many combinations are possible. Those skilled inthe art can determine which of the many combinations are most suitablefor a desired design. Combining the readings from a variety of differentcombinations of readings, including both differential andnon-differential readings, may provide composite readings that maydetect more deeply, with more accuracy, and less noise.

In some embodiments the detector 10 uses a single capacitance-to-digitalconverter 38. In some embodiments the sensor plates 32 may beindividually connected to the capacitance-to-digital converter 38. Insome embodiments the sensor plates 32 may be individually connected tothe capacitance-to-digital converter 38 via a multiplexer 37. In someembodiments more than one sensor plate may be connected to thecapacitance-to-digital converter 38 at a time. In some embodimentsmultiple adjacent sensor plates 32 may be connected to thecapacitance-to-digital converter. In some embodiments multiplenon-adjacent sensor plates 32 may be connected to thecapacitance-to-digital converter. The use of a multiplexer 37 to connectsensor plates 32 to a single capacitance-to-digital converter mayimprove the sensor plate to sensor plate 32 consistency of the readings,because the readings from each of the sensor plates 32 may be equallyaffected by variations to the capacitance-to-digital converter 38.Factors that may affect the readings from capacitance-to-digitalconverter 38 may include, but are not limited to process variations,temperature variations, voltage variations, electrical noise, aging, andothers.

In some embodiments a detector 10 may use more than onecapacitance-to-digital converter 38. In some embodiments that use morethan one capacitance-to-digital converter 38 methods of calibrating thedifferent capacitance-to-digital converters 38 to each other areemployed. In some embodiments each of the individualcapacitance-to-digital converters 38 are configured so that they mayeach read a common calibration capacitance. The calibration capacitancemay be a discrete capacitor, or it may be traces on the printed circuitboard 40, or another capacitance. After each capacitance-to-digitalconverter 38 reads the common calibration capacitance then calibrationvalues are determined. The calibration values can be combined with thereadings to bring the readings from the different capacitance-to-digitalconverters 38 in harmony with each other.

In some embodiments with multiple capacitance-to-digital converters 38,the capacitance-to-digital converters 38 can be calibrated to each otherby having the sensor plates 32 read the capacitance of a common surface,either through the same sensor plate 32, or through different sensorplates 32. This could be accomplished, for example, by placing sensorplates 32 over a uniform surface. Differences in readings wouldpresumably be due to differences in the capacitance-to-digitalconverters 38. After each capacitance-to-digital converter 38 reads thecommon surface then calibration values are determined. The calibrationvalues can be combined with the readings to bring the readings from thedifferent capacitance-to-digital converters 38 in harmony with eachother.

In some embodiments, the sensor plate traces 35 are routed such thateach of the sensor plate traces 35 have substantially equal capacitance,resistance, and inductance. In some embodiments it is desirable for eachof the sensor plate traces 35 to have the same electrical properties, sothat each of the sensor plates 32 will respond equivalently to the samedetected objects.

In some embodiments each of the traces 35 from thecapacitance-to-digital converter 38 to each of the sensor plates 32 hassubstantially the same length, as shown in FIG. 7. In some embodimentstwo or more of the sensor plate traces 35 from thecapacitance-to-digital converter 38 to the sensor plates 32 hassubstantially the same length. Sensor plate traces 35 with substantiallythe same length may have more equivalent capacitances, inductances, andresistances. Equal length sensor plate traces 35 may offer enhancedperformance because they may improve the uniformity of the readings,such that the sensor plates 32 respond more equivalently to the samedetected objects, and may provide more immunity from environmentalconditions, such as temperature.

In some embodiments each of the sensor plate traces 35, that compriseelectrically conductive paths, have substantially the same width. Insome embodiments, both the width and the length of each of the sensorplate traces 35 are made to be equivalent. In some embodiments thesensor plate traces 35 will have more than one segment. For example, afirst segment of the traces may route the sensor plate traces 35 from acapacitance-to-digital converter 38 to a via. The via may take thesensor plate trace 35 to a different layer of the printed circuit board40, where there may be a second segment of the sensor plate trace 35. Insome embodiments all of the sensor plate traces 35 will have the samelength and width, in each segment, as the other traces in that segment.In some embodiments two or more of the sensor plate traces 35 will havethe same width throughout a first segment. In some embodiments two ormore of the sensor plate traces 35 will have the same width throughout asecond segment. In some embodiments two or more of the sensor platetraces 35 will have the same length throughout a first segment. In someembodiments two or more of the sensor plate traces 35 will have the samelength throughout a second segment.

In some embodiments each of the traces 35 from thecapacitance-to-digital converter 38 to each of the sensor plates 32 hassubstantially the same surroundings. In some embodiments the sensorplate traces 35 are routed sufficiently far apart so that capacitive andinductive coupling between traces 35 is minimized, and may improveconsistency because each of the sensor plate traces 35 may havesurroundings that are more similar to the other sensor plate traces 35.In some embodiments, as shown in FIG. 7, each of the sensor plate traces35 are shielded on one or both sides with a shield trace 99. In someembodiments the shield trace 99 is routed at a uniform distance from thesensor plate traces 35 on both sides of each sensor plate trace 35. Insome embodiments the shield traces 99 are parallel to the sensor platetraces 35.

In some embodiments, the shield traces 99 are substantially parallel tothe sensor plate traces 35. In some embodiments, the shield traces 99are positioned such that the shield traces 99 shield the sensor platetraces 35 from external electromagnetic fields. In some embodiments, twoor more sensor plate traces 35 have one or more respective shield traces99. In some embodiments, the sensor plate traces 35 and shield traces 99are positioned such that capacitance between each sensor plate trace 35and each respective shield trace 99 is substantially the same for eachsensor plate trace 35 and its respective shield trace 99. In someembodiments a sensor plate trace 35 is accompanied by two shield traces99, such that one shield trace is positioned on each side of the sensorplate trace. In some embodiments, a sensor plate trace 35 and a shieldtrace 99 are positioned such that there is a constant distance between asensor plate trace 35 and the respective shield trace 99, along theirlength. In some embodiments each of the shield traces 99 are positionedat a uniform distance away from the respective sensor plate trace 35. Insome embodiments a segment of the each sensor plate trace 35 and asegment of each shield trace 99 comprise copper traces on a printedcircuit board 40. In some embodiments, the sensor plate traces 35 andshield traces 99 are both located on the same layer of a printed circuitboard 40. In some embodiments, the shield traces 99 are driven at afixed voltage level. In some embodiments, the shield traces 99 aredriven at a voltage that is similar to the voltage driven on the firstset of electrically conductive paths.

In some embodiments the shield traces 99 may be routed at a distance ofapproximately 0.6 mm from each sensor plate trace 35, along as much ofthe length of the sensor plate trace 35 as is possible. In someembodiments the sensor plate traces 35 are approximately 0.15 mm widethroughout one segment of the sensor plate trace 35.

In some embodiments the sensor plate traces 35 comprise multiplesegments. In some embodiments a segment of a sensor plate trace 35 maybe the wire bonds that are within the package of an integrated circuitthat route the signals from the piece of silicon to the pins of theintegrated circuit package. In some embodiments a segment of a sensorplate trace 35 may comprise a layer of copper on a first layer of aprinted circuit board 40. In some embodiments a segment of a sensorplate trace 35 may comprise a layer of copper on a second layer of aprinted circuit board 40.

In some embodiments the sensor plate traces 35 are shielded with layersof copper, such that the traces 35 are shielded both on a layer abovethe sensor plate traces 35, and are shielded on a layer below the sensorplate traces 35.

In some embodiments the shield traces 99 that are used for shielding maybe driven at a fixed voltage value. In some embodiments the shieldtraces 99 may be driven with a signal that has a voltage that is similarto the signal that is driven on the sensor plates 32, or to anothervalue. Serpentine routing may be used so that all of the sensor platetraces 35 may have the same length.

In one particular example, the obscured feature detector 10 comprisesthirteen sensor plates 32 arrayed side by side in vertical orientationalong the longitudinal axis of the detector 10, with a gap ofapproximately 1.7 mm between adjacent plates. In this particularexample, each sensor plate 32 has a width of about 11 mm wide and alength of about 47 mm. In some embodiments two or more sensor plates 32have the same length. In some embodiments two or more sensor plates 32have the same width. In some embodiments two or more sensor plates 32have the same thickness.

The housing 12 can be manufactured from ABS plastic. In order toaccommodate the thirteen sensor plates 32, the housing 12 can have alength of about seven inches and a width of about three inches.

In some embodiments, the housing 12 has a longitudinal axis with alength of at least about 6″, which advantageously enables the obscuredfeature detector 10 to span the full width of a common obscured feature,such as a stud 95, from a stationary position. By contrast, manyexisting stud detectors are not wide enough to span the full width of astud 95 without being moved.

In other embodiments, the obscured feature detector 10 can be longerthan 16″, with about thirty sensor plates 32, or more. Such aconfiguration can be particularly advantageous, because many structuresbuilt according to standard construction methods in the United Stateshave studs 95 spaced 16″ apart on center. Thus, whenever an obscuredfeature detector 10 having a length greater than about 16″ is placedagainst a wall of such a structure, the detector 10 will typicallyindicate the presence of at least one stud 95 on the first try.

In some embodiments the width of obscured features are identified. Someembodiments have sensor plates 32 that are spread over a distance thatis wider than the detected obscured features. In some embodiments thedetector activates all of the indicators 52 that are in front of anobscured feature, the activated indicators 52 indicate the position andwidth of the obscured features. In some embodiments an activatedindicator indicates that there is an obscured feature behind theactivated indicator. In some embodiments, the width of the set ofactivated indicators 52 indicates the width of the obscured feature. Insome embodiments, the width of a continuous set of activated indicators52 indicates the width of the obscured feature.

For example, to indicate that a three inch wide beam has been detectedall the indicators 52 that are in front of the beam are activated, suchthat a continuous set of indicators 52 are activated over a 3 inch span,directly in front of the beam. Likewise, to indicate that a one and ahalf inch wide stud 95 has been detected the indicators 52 that are infront of the stud 95 are activated, such that a continuous set ofindicators 52 are activated over a one and a half inch span directly infront of the beam. Some embodiments have indicators 52 that are spacedone half inch apart and identify the width of obscured features with agranularity of one half inches. Some embodiments identify the width ofobscured features with a granularity of one half inches. Someembodiments have a minimum feature size of one and half inches and agranularity of one half inch, for features that are wider than one andone half inch. Many other combinations of minimum features size andgranularity are possible. In some embodiments the width of multipleobscured features can be identified by multiple sets of activatedindicators 52.

Advantageously, the present disclosure provides various embodiments of asurface-conforming obscured feature detector 10. Conventional detectorshave sensor plates 32 that are rigidly connected together, and as aresult the size of obscured feature detectors typically remainsrelatively small to function on the curved surfaces that are typical ofmany architectural surfaces. The surface-conforming feature detector 10disclosed herein conforms to the contour of the surface, minimizes airgaps, and makes it possible to build larger feature detectors that canoffer a variety of performance improvements. The improvements describedin the present disclosure are applicable to both conventional detectorsthat are relatively small, and to larger feature detectors.

Viewing FIGS. 2 and 3, in some embodiments, the obscured featuredetector 10 has one or more flexible printed circuit boards 40 that canbend to match the contour of the surface to be detected. The flexibleprinted circuit boards 40 comprise a flexible substrate. Other flexiblesubstrates can also be used that can be made of wood, paper, plastic, orother flexible materials. Rigid flex printed circuit boards 40 can alsobe used.

The one or more printed circuit boards 40 can be flexibly connected tothe housing 12 using a flexible medium such as foam rubber, springs,gel, hinges, pivot points, an encapsulated gas such as air, or othersuitable compressible or flexible media. In some embodiments the housing12 is able to flex. In some embodiments the housing 12 is partiallyflexible. In some embodiments the housing 12 has integrated plastic leafsprings, or other types of springs or features that provide flexibility.In some embodiments of the obscured feature detector 10, the sensorplates 32 can be mounted on a printed circuit board 40 that is mountedexternal to the housing 12, as seen in FIGS. 2 and 3. In someembodiments the printed circuit board 40 is connected to the housing 12via a foam rubber ring 70. In some embodiments, the foam rubber ring 70is about seven millimeters thick and is formed approximately in theshape of a ring that is about six millimeters wide along the long side,and about five millimeters thick along the short side, and approximatelyfollows the perimeter of the housing 12. A permanent adhesive, such as apressure sensitive acrylic adhesive, can be used to bond the foam rubberring 70 to the housing 12 and to the printed circuit board 40.

In some embodiments, the foam rubber ring 70 is compressible, and theprinted circuit board 40 is flexible, allowing the obscured featuredetector 10 to conform to curvature and irregularities of a surfaceagainst which it is placed. A variety of flexible and/or compressiblematerials can be suitable for the flexible medium. EPDM foam rubber thatis rated for 25% compression under about 1.5 pounds per square inch ofpressure can be used. Other types of foam rubber such as polyurethanefoam or silicon rubber foam can also be used. In some embodiments it isdesirable that the flexible medium attached between the printed circuitboard substrate and the housing 12 not be electrically conductive orpartially conductive, at least not to the extent that it would interferewith to operation of the detector 10.

FR-4 and Rogers 4003, and other printed circuit board substrates havesufficient flexibility to bend to match the contour of manyarchitectural surfaces. In some embodiments that use FR-4, a variety ofFR-4 with a high dielectric breakdown can be used to protect fromelectrostatic discharge. S1141 from Guangdong Shengyi has a dielectricbreakdown of greater than 40 kV/mm which provides good electro-staticdischarge protection, compared to some versions of FR-4, which may havea typical dielectric breakdown of about 20 kV/mm. Many varieties of FR-4may be suitable.

In some embodiments a 1.6 mm thick printed circuit board 40 with fourlayers of copper can be used. As illustrated in FIG. 19 the first layerof copper is on the upper surface and all of the electrical componentsare soldered to this layer. The second layer of copper can be at aposition that is about 0.35 mm below the first layer of copper, suchthat there is about 0.35 mm of printed circuit board substrate betweenthe first and second layers of copper. The third layer of copper can beat a position that is about 0.1 mm below the second layer of copper,such that there is about 0.1 mm of printed circuit board substratebetween the second and third layers of copper. A fourth layer of coppercan be at a position that is about 0.35 mm below the third layer ofcopper, such that there is about 0.1 mm of printed circuit boardsubstrate between the third and fourth layers of copper. In someembodiments all the vias can be drilled to connect the four layers ofcopper.

In some embodiments a final layer of substrate material that is 0.8 mmthick can be placed to cover the fourth layer of copper. In someembodiments, no holes are drilled through the 0.8 mm thick layer ofsubstrate. The 0.8 mm thick layer of substrate may help protect thecircuit from electrostatic discharge. Alternatively, a layer of plastic,or other non-conductive material, can be used to shield the circuit fromelectrostatic discharge and to physically protect the printed circuitboard 40. In some embodiments, a layer of plastic can be used inaddition to a protective layer of circuit board substrate. It is to beunderstood that the v layers and thicknesses indicated here are onlyexemplary of one embodiment. Other combinations of layers andthicknesses, and materials, can also be used.

In some embodiments the sensor plates 32 can be placed on the fourthlayer of copper. A shield to electrically protect the sensor plates 32from electrical interference from ambient conditions, including theuser's hand may be used. In some embodiments the shield may be placed onthe first layer of copper. In some embodiments a solid shield the coverssubstantially all of the shield's area, instead of using a mesh, orstripes, or another pattern that may provide less than substantially allof the shield's area.

In some embodiments the electrically conductive paths that link thesensor plates 32 to the capacitance-to-digital converter 38 comprisesensor plate traces 35. In some embodiments the sensor plate traces 35are placed primarily on the second layer of copper, and shields for the35 are placed on the first and fourth layers of copper.

In some embodiments each sensor plate 32 may be on its own independentprinted circuit board 40. In some embodiments each sensor plate 32 canbe individually attached to the housing 12 through a flexible mediumsuch as a spring, or foam rubber. In some embodiments the sensor plates32 are on plastic, wood, or other appropriate materials.

In some embodiments, the obscured feature detector 10 uses a pluralityof printed circuit boards 40 that can each be independently, flexiblyconnected to the detector housing 12.

The sensor plates 32 can be mounted on two independent printed circuitboards 40, such that approximately half of the sensor plates 32 are on afirst printed circuit board 40, and approximately half of the sensorplates 32 are on a second printed circuit board 40. In this way, it maybe possible to achieve a design that offers increase surface conformingcapability. In some embodiments more than two independent circuit boards40 are used.

In some embodiments, the housing 12 has flexible features that allow thehousing 12 to flex or bend to adapt to the contour of a non-flatdetecting surface. In one particular example, an obscured featuredetector 10 uses two printed circuit boards 40. Each printed circuitboard 40 is attached to the housing 12. In this particular example, thehousing 12 is able to flex in the center, such that each sensor plate 32more closely matches the contour of the surface to be detected. In someembodiments, the housing 12 is mostly or entirely flexible.

In some embodiments the integrated circuits that are soldered to theprinted circuit board 40 are covered with a layer of epoxy, or a glob ofepoxy, or another conformal coating which may improve the reliability ofsolder joints. In some embodiments the integrated circuits on theprinted circuit board 40 are wire bonded to the printed circuit board 40with chip on board technology. The chip on board technology normallyinvolves the steps of (1) attaching bare die to the printed circuitboard 40, (2) wire bonding (electrically connecting signals on the baredie to the printed circuit board 40), and (3) covering the bare die andwire bonds with a coating of epoxy, or other appropriate material. Thechip on board technology may improve the reliability of solder joints.In some embodiments, some of the integrated circuits that have solderreliability issues are placed on a printed circuit board 40 that isseparate from the printed circuit that contains the sensor plates 32. Insome embodiments all of the integrated circuits and other electroniccomponents are placed on a printed circuit board 40 that is separatefrom the printed circuit board 40 that contains the sensor plates 32.

In some embodiments a ribbon cable is soldered to the printed circuitboard 40 with the sensor plates 32 to connect it to a printed circuitboard 40 with the integrated circuits. A soldered-down ribbon cable,such as the flat flexible cable from Parlex, may provide a reliableconnection to connect printed circuit boards 40 that experience flexingand bending. In some embodiments integrated circuits that have packageswith external leads are used such as QFP packages, TSOP packages, SOICpackages, QSOP packages, or others. Components that have external leadsmay provide improved the solder joint reliability, as compared topackages without external leads, such as QFN packages, or BGA packages.In some embodiments leadless packages, such as QFN packages and BGApackages, are used and the connection between the packages and the PCBis reinforced using an epoxy covering, commonly referred to as aglob-top.

In some embodiments, the obscured feature detector 10 can be operated ina first mode suitable for detecting obscured features through a thinsurface that may correspond to a thin piece of sheet rock, or a secondmode suitable for detecting obscured features through thick surface thatmay correspond to a thick piece of sheetrock 80.

In some embodiments there may be one set of patterns that may beoptimized for a first surface thickness, and another set of patternsthat may be optimized for a second surface thickness. Embodiments thatare able to select the thickness of the surface material may haveoptimized detection capabilities, over embodiments with patterns thatare not optimized for a particular surface material.

In some embodiments, the sensor plates 32 that are near the middle ofthe detector 10 may respond differently than sensor plates 32 that arenear the edges of the detector 10. The response of the sensor plates mayvary depending upon the thickness of the surface.

Some embodiments that have more than one mode for selecting thethickness are better able to calibrate the readings, and provide moreaccurate readings. Embodiments that have more than one surface thicknessselection mode may be able to detect features more deeply. Embodimentsthat have more than one surface thickness detection mode may be able todetect the position of features more accurately.

In some embodiments, the obscured feature detector 10 can operate in afirst mode that may be more suitable for detecting through a firstsurface type, or in a second mode that may be more suitable fordetecting through a second surface type. In some embodiments the firstsurface type may be a surface with a low dielectric constant, such assheetrock 80. In some embodiments the second surface type may be asurface with a higher dielectric constant such as wood.

In some embodiments there may be one set of predetermined patterns thatmay be optimized for the first surface type, and another set of patternsthat may be optimized for the second surface type. Embodiments that areable to select the nature of the surface material may have optimizeddetection capabilities, over embodiments with patterns that are notoptimized for a particular surface material.

In some embodiments, the sensor plates 32 that are near the middle ofthe detector 10 may respond differently than sensor plates 32 that arenear the edges of the detector 10. The response of the sensor plates 32near the edges of the detector 10, compared to the response of sensorplates 32 near the middle of detector 10, may vary depending upon thesurface material. In some embodiments the calibration procedure may beoptimized for the surface type. Embodiments that have more than one modefor selecting the surface type may be able to better calibrate thereadings, and provide more accurate readings. Embodiments that have morethan one mode for selecting the surface type may be able to detectfeatures more deeply. Embodiments that have more than one mode forselecting the surface type may be able to detect the position offeatures more accurately.

In some embodiments the mode is selected via an actuator. In someembodiments the mode is set by the controller 60. In some embodimentsthe mode is set by the controller 60 automatically. In some embodimentsthe mode is set by the controller 60 automatically after thecapacitances have been read.

In some embodiments, the obscured feature detector 10 can be operated ina first mode suitable for detecting an obscured feature that is embeddedwithin a material, such as detecting a pipe within concrete, or a secondmode suitable for detecting when the obscured feature is located on theother side of a surface, such as detecting a stud 95 on the other sideof a piece of sheetrock 80.

In some embodiments the detector 10 may decide whether an obscuredfeature is present by analyzing the disparity in the measuredcapacitance readings. In some embodiments, a disparity value thatreflects that amount of disparity in the measured capacitance readingsis determined.

In some embodiments the measured capacitance readings are compared, andif the disparity value exceeds a feature-detection threshold then thedetector 10 may determine that at least one obscured feature is present.In some embodiments the detector 10 may determine that an obscuredfeature is present if the disparity value, determined by comparing twoor more measured capacitance readings exceeds a feature-detectionthreshold. In some embodiments the detector 10 determines that anobscured feature is present if the difference between the largestmeasured capacitance readings and the smallest measured capacitancereading exceeds a feature-detection threshold.

In some embodiments, the obscured feature detector 10 has a first modethat has a higher feature-detection threshold, and a second mode with alower feature-detection threshold. In the first mode the detector 10 mayrequire a clearer signal before the detector 10 indicates the locationof an obscured feature. The second mode, with a lower feature-detectionthreshold may indicate the location of more subtle features that may notbe detected in the first mode. The low threshold mode may make itpossible to detect features that are deeper. However the second mode,with a lower feature-detection threshold, may be more inclined tofalsely indicate a feature that may not be present.

In some embodiments the mode is selected via an actuator. In someembodiments the mode is set by the controller 60. In some embodimentsthe mode is set by the controller 60 automatically. In some embodimentsthe mode is set by the controller 60 automatically after thecapacitances have been read.

In some embodiments, the obscured feature detector 10 can operate in afirst mode that may be more suitable for detecting obscured featuresthat comprise a first material, or in a second mode that may be moresuitable for detecting obscured features that comprise a secondmaterial.

In some embodiments, the obscured feature detector 10 can operate in afirst mode that may be more suitable for detecting wooden obscuredfeatures, such as wood beams or wood studs 95, or in a second mode thatmay be more suitable for detecting metallic features, such as a metalstuds 95 or metal beam.

In some embodiments there is a set of predetermined patterns that havevalues that are consistent with the detector 10 sensing wooden obscuredfeatures. In some embodiments there is a set of predetermined patternsthat have values that are consistent with the detector 10 sensingmetallic obscured features. In some embodiments there is a set ofpredetermined patterns that have values that are consistent with thedetector 10 sensing plastic obscured features.

Embodiments that are able to select the nature of the detected obscuredfeatures may have optimized detection capabilities, over embodimentsthat are not optimized for a particular obscured feature material.

In some embodiments, the first mode, or second mode, can be selected viaan actuator. In some embodiments the controller 60 sets the mode. Insome embodiments the controller 60 automatically selects the mode. Insome embodiments, the controller 60 automatically selects the mode afterthe capacitances have been measured at least once.

In some embodiments the obscured feature detector 10 has a deep sensingmode that may provide deeper sensing, and a second high accuracy modethat may provide more accurate resolution of feature positions. In someembodiments the deep sensing mode may be implemented by electricallyconnecting sensor plates 32 in groups of two, three or more in a rollingsweep, thereby effectively increasing the sensor plate 32 size. Insingle-plate mode only one sensor plate 32 may be activated at a time,which may provide more accurate determination of feature positions.

In some embodiments the obscured feature detector 10 has a normaloperating mode that is suitable for detecting one or a plurality offeatures, and an alternate, single feature detection mode that onlyindicates the position of a single obscured feature.

Some embodiments of the single feature detection mode will activateindicator(s) that correspond to the single highest sensor plate reading,the highest plate being selected after all readings have beencalibrated. Some embodiments of the single-object detection mode may usea pattern matching module that only searches for single obscuredfeatures.

In some embodiments, a module that only indicates the location of asingle feature may be able to operate at a lower detection threshold,which may make it possible to find features that would be below thenoise threshold in the normal operating mode. A module that onlyindicates the location of a single feature may provide more consistentreadings on some materials. A module that only indicates the location ofa single feature may provide the user with better readings on somematerials.

In some embodiments, the obscured feature detector 10 has a fastdetection mode that may provide quicker detection and may providequicker updates to the indicators 52, but may provide less accuracy andmay provide less deep detection, and a slow detection mode that mayprovide slower detection but may be able to sense more deeply or moreaccurately.

In some embodiments the fast detection mode uses fewer readings tocreate the sensor plate readings. For example in some embodiments thefast detection mode creates a reading by summing twelve readings of thesensor plates 32.

In some embodiments the slow detection mode uses more readings to formthe sensor plate readings. For example in some embodiments the slowdetection mode creates a reading by summing twenty-four readings of thesensor plates 32.

In some embodiments the obscured feature detector 10 has a mode fordetecting live wires, such as 50 Hz and 60 Hz wires that may carry 115V,230V, or other voltages.

In some embodiments the capacitance-to-digital converter 38 reads eachof the sensor plates 32 at least approximately six times per cycles.This implies that it reads the sensor plates 32 at least approximately360 times per second, to detect 60 Hz. Reading the sensors plates atleast six times per second may provide readings that approximatelyreflect all of the phases of the cycle. In some embodiments the sensorplates 32 are read more than six times per cycle, which may provideimproved performance. In some embodiments regions with more disparity inthe readings are identified as regions that are closer to an alternatingelectromagnetic field.

In some embodiments the sensing circuit performs capacitive readings ata frequency that is an inharmonic of the detected electromagnetic fieldfrequency, and may provide readings that approximately reflect all ofthe phases of the cycle. In some embodiments the sensing circuitperforms capacitive readings at a higher frequency than the detectedelectromagnetic field frequency. In some embodiments the sensing circuitperforms capacitive reads at least approximately 150 times per second.

In some embodiments the detector 10 compares the readings from thedifferent segments of the cycle. The sensor plate 32 readings that havethe most disparity may be nearest to live wires. In some embodiments thedetector 10 compares multiple capacitive readings from a single regionto determine the amount of disparity in the readings for each respectiveregion. For example multiple readings from a first region may becompared to each other readings from the first region to create a valuethat reflects the amount of disparity in the readings in the firstregion. Likewise, multiple readings from a second region may be comparedto each other to create a value that reflects the amount of disparity ofthe readings in the second region. Similar readings may be made for eachregion, and a value that reflects the amount of disparity may bedetermined for each respective region.

To decide which indicators 52 to activate, in some embodiments, the samemodules that are used to determine the location of obscured features canbe adjusted by those skilled in the art to determine the location oflive wires.

In some embodiments values that represent the disparity in thecapacitance readings comprise a disparity reading pattern; a patternmatching module is configured to compare the disparity reading pattern,with a plurality of predetermined electromagnetic field patterns todetermine which predetermined electromagnetic field pattern best matchesthe disparity reading pattern. In some embodiments a set of indicators52 are associated with each predetermined electromagnetic field pattern.In some embodiments the indicators 52 that are associated with thebest-matching electromagnetic field pattern are activated. Those skilledin the art can modify the pattern matching module that detects obscuredfeatures, so that it identifies the location of electromagnetic fieldsthat are associated with live wires.

In some embodiments the region that has the highest disparity reading isidentified as the region that is closest to an electromagnetic fieldthat is associated with live wires, if the reading exceeds a thresholdvalue.

In some embodiments of the detector 10 the indicators 52 that are usedto detect the position of an obscured features are the same indicators52 that are used indicate the location of electromagnetic fields. Inanother embodiment one set of indicators 52 is used to indicate thelocation of electromagnetic fields, and a second set of indicators 52 isused to indicate the position of obscured features.

In some embodiments the live wire detection runs simultaneous withobscured feature detection. In some embodiments the detector 10 providesan alert to warn that live wires are being detected. In some embodimentsindicators 52 may flash to indicate that live wires are being detected.In some embodiments indicators 52 may change to a different state toindicate that live wires are being detected. In some embodiments theindicators 52 may comprise LEDs (Light Emitting Diodes) that may changeto an alternate color to indicate the proximity to a live wire. In someembodiments the obscured feature detector 10 has a first mode that issuitable for detecting the location obscured features, and a second modethat is suitable for detecting the presence of the electromagneticfields that are associated with live wires. In some embodiments thedetector 10 is optimized to detect electromagnetic fields with afrequency of approximately 50 to 60 Hz.

In some embodiments, as shown in FIG. 18, a layer of protective material49 is mounted to the bottom of the detector 10, such that there is alayer of protective material 49 between the wall and the detector 10.The protective material 49 that has the interior substantially filled upsuch that it is substantially free from cavities, such as plastic. Theprotective material 49 is unlike felt, velcro, cloth, or other materialsthat have an interior with cavities. The layer of protective material 49may serve the purpose of protecting the bottom of the detector 10 fromdamage due to knocks, bumps, and wear-and-tear. The protective material49 could be made from a solid piece of material, such as plastic orother solid non-conductive materials. A solid layer of plastic mayprovide a low friction surface that would allow the detector 10 to slideacross the wall. Although some embodiments of the detector 10 do notrequire sliding or operate, low friction may be useful to some usersthat may choose to move the detector 10 from position-to-position bysliding it.

The protective layer of plastic may be mounted with a pressure sensitiveadhesive, glue, or other means. The layer of protective material 49 maybe a complete layer that covers the entire surface; it may berectangular strips, round pieces, or other layers of plastic with othergeometries.

A protective material 49 that is substantially filled up such that it issubstantially free from cavities may build up less static charge thanprior art solutions and may advantageously provide for more consistentreadings.

In some embodiments the protective material 49 is UHMW-PE (Ultra-HighMolecular Weight Polyethylene). UHMW-PE has a low coefficient offriction. UHMW-PE also absorbs very little moisture which may provideincreased immunity from changes in humidity, and may provide enhancedimmunity from changes in humidity.

In some embodiments the obscured feature detector 10 can make a mark onthe detected surface to indicate the location of obscured features. Someembodiments use a marker, such as a pencil-type marker to mark thelocation of obscured features. Some embodiments provide for multiplemarkers, that may be positioned a various positions along the length ofthe detector 10, whereby a marker may be located at each position wherea mark may need to be made. Of the plurality of markers, only themarkers that are in a location where a mark is desired are activated.

Some embodiments of the obscured feature detector 10 provide a singlemarker that can be moved to the position of an obscured feature. In someembodiments the marker uses graphite, similar to the graphite found in apencil. Graphite-type marking methods are robust, well-proven, don't dryup, and can easily be erased from the surface. In other embodimentsother types of marking materials are used.

Some embodiments may indicate the presence of features that may be solarge that substantially all of the sensor plates 32 may be over afeature. Features that are this large may be called large features 96,or large obscured features 96. If the detector 10 is initially placedover a large feature 96, such that substantially all of the sensorplates 32 are over the large feature 96, all of the readings from thesensor plates 32 may have substantially the same value. This may causethe detector 10 to indicate that there are not any obscured featurespresent. However, some embodiments provide a module that allows theobscured feature detector 10 to indicate the presence of features thatare so large that substantially of the sensor plates 32 may be over thefeature.

In some embodiments, when it is determined that there is an obscuredfeature in a particular region, a memory will record the value of thecapacitance reading that existed at the time that the obscured featurewas present. Then, subsequently if it is determined that a newcapacitance reading has a value that is near the value stored in memory,then the indicators 52 associated with the respective region(s) may beactivated. The procedure may allow the detector 10 to activateindicators 52 even when at least most of sensor plates 32 are over afeature.

In some embodiments, the detector 10 may indicate that it is over alarge obscured feature 96 if the detector 10 first determines that thedetector 10 is over region where a large feature 96 may be present, thenif subsequently all of the sensor plate readings are substantiallysimilar. FIG. 16 illustrates an obscured feature detector 10 that ispartially over a large feature 96; the detector 10 has some of theindicators 52 activated. The detector 10 may be approaching a regionwhere a large feature 96 may be present.

In some embodiments, the detector 10 may decide that a very largeobscured feature 96 is present if an increasing number of indicators 52become activated, increasing in number from one side of the detector 10to the other. In some embodiments, the detector 10 may indicate that itis over a large obscured feature 96, if it was previously over regionwhere a large feature 96 may be present approaching a large feature 96,then subsequently all of the sensor plate readings are substantiallysimilar, and if the sensor plate readings are above a threshold value.

In some embodiments the detector 10 may indicate that it is over a largeobscured feature 96 if in a first time period many of the indicators 52are activated and if in a second time period all of the sensor platereadings are substantially similar. In some embodiments the detector 10may indicate that it is over a large obscured feature 96 if all of thesensor plate readings are substantially similar and if the sensor platereadings are above a threshold value. In some embodiments the detector10 may indicate that it is over a large obscured feature 96 if in afirst time period the detector 10 had an indication that it was overregion where a large feature 96 may be present and if in a second timeperiod all of the sensor plate readings are substantially similar.

In some embodiments the detector 10 may indicate that it is over a largeobscured feature 96 if in a first time period the detector 10 sensedcapacitive readings that are consistent with the detector 10 being neara large obscured feature 96 and if in a second time period all of thesensor plate readings are substantially similar. In some embodiments thedetector 10 may indicate that it is over a large obscured feature 96 ifin a first time period the detector 10 sensed capacitive readings thatare consistent with the detector 10 being near a large obscured feature96 and if in a second time period all of the sensor plate readings aresubstantially similar. In some embodiments the detector 10 may indicatethat it is over a large obscured feature 96 if in a first time periodthe detector 10 sensed capacitive readings that are consistent with thedetector 10 being near a large obscured feature 96 and if in a secondtime period one or more of the sensor plates 32 are above a thresholdvalue. In some embodiments, the detector 10 may activate all of theindicators 52 to indicate that the detector 10 is over a large obscuredfeature 96. FIG. 17 illustrates an obscured feature detector 10 that isover a large feature 96; the detector 10 has all of the indicators 52activated.

What is claimed is:
 1. An obscured feature detector comprising: aplurality of sensor plates, each having a capacitance that varies basedon: (a) the proximity of the sensor plate to one or more surroundingobjects, and (b) the dielectric constant(s) of the surroundingobject(s); a sensing circuit coupled to the sensor plates, the circuitbeing configured to measure the capacitances of the sensor plates withthe obscured feature detector in a stationary position, the set ofmeasured capacitance values comprising a measured reading pattern; acontroller comprising non-volatile memory storing a predeterminedreading pattern comprising a plurality of capacitance values, and apattern matching module configured to compare the measured readingpattern with the predetermined reading pattern, and determine whetherthe predetermined reading pattern matches the measured reading pattern;and one or a plurality of indicators coupled to the controller, eachindicator capable of toggling between a deactivated state and anactivated state, wherein the controller is configured to activate one ormore of the indicators to identify a location of an obscured feature. 2.The obscured feature detector of claim 1, wherein the predeterminedreading patterns has values that are consistent with the detectorperforming a reading on sheetrock with a single stud behind thesheetrock.
 3. The obscured feature detector of claim 1, wherein thepredetermined reading patterns has values that are consistent with thedetector performing a reading on sheetrock with two studs behind thesheetrock, the two studs separated by a distance of at least about twoinches.
 4. The obscured feature detector of claim 1, wherein theobscured feature detector comprises at least four sensor plates.
 5. Theobscured feature detector of claim 1, wherein the indicators are LEDs.6. The obscured feature detector of claim 1, wherein the patternmatching module is configured to compare the values of the measuredreading pattern to the values of the predetermined reading pattern. 7.The obscured feature detector of claim 1, wherein the pattern matchingmodule is configured to compare the slopes of the measured readingpattern to the slopes of the predetermined reading pattern, wherein theslopes of the measured reading pattern are calculated by comparingneighboring measured capacitance values and the slopes of thepredetermined reading pattern are calculated by comparing neighboringvalues.
 8. The obscured feature detector of claim 1, wherein thepredetermined reading pattern comprises a plurality of predeterminedreading patterns comprising at least 30 unique reading patterns.
 9. Theobscured feature detector of claim 1, wherein each of the sensor platesare substantially the same size.
 10. The obscured feature detector ofclaim 8, wherein the plurality of predetermined reading patternsincludes multiple reading patterns corresponding to a single stud, whereeach of the multiple reading patterns corresponds to a single stud in adifferent location.
 11. The obscured feature detector of claim 1,wherein the non-volatile memory stores a plurality of predeterminedreading patterns.
 12. The obscured feature detector of claim 8, whereinthe pattern matching module is configured to calculate the plurality ofpredetermined reading patterns and store them in memory when theobscured feature detector is initialized.
 13. The obscured featuredetector of claim 8, wherein the pattern matching module is configuredto calculate the plurality of predetermined reading patterns and storethem in memory when a calibration routine in executed.
 14. The obscuredfeature detector of claim 8, wherein the pattern matching module isconfigured to calculate the plurality of predetermined reading patternsin real-time, when the obscured feature detector is in use.
 15. A methodfor determining the location of obscured features behind a surface, themethod comprising: placing an obscured feature detector in a stationaryposition on the surface, the obscured feature detector having aplurality of sensor plates arranged in an array; measuring capacitancereadings sensed in a plurality of regions, each region corresponding toan area surrounding one or more of the sensor plates, the set ofcapacitance readings forming a measured reading pattern; comparing themeasured reading pattern to each of a plurality of predetermined readingpatterns, each predetermined reading pattern comprising a set ofcapacitance values and being stored in non-volatile memory in acontroller; identifying, based upon comparisons of the measured readingpattern to the predetermined reading patterns, the predetermined readingpattern that best matches the measured reading pattern, eachpredetermined reading pattern being associated with one or moreindicators; and activating the one or more indicators associated withthe predetermined reading pattern that best matches the measured readingpattern.
 16. The method of claim 15, wherein at least one of thepredetermined reading patterns has values that are consistent with thedetector performing a reading on sheetrock with a single stud behind thesheetrock.
 17. The method of claim 15, wherein at least one of thepredetermined reading patterns has values that are consistent with thedetector performing a reading on sheetrock with two studs behind thesheetrock, the two studs being located adjacent to each other.
 18. Themethod of claim 15, wherein at least one of the predetermined readingpatterns has values that are consistent with the detector performing areading on sheetrock with two studs behind the sheetrock, the two studsbeing separated by a distance of at least about two inches.
 19. Themethod of claim 15, wherein at least one predetermined reading patternis associated with one or more indicators spanning a distance of atleast about one and one half inches.
 20. The method of claim 15 whereinat least one predetermined reading pattern is associated with one ormore indicators that indicate the edges of an obscured feature.